Method for acquiring cross-domain separation paths, path computation element and related storage medium

ABSTRACT

A method for acquiring a cross-domain separation path includes: when receiving a cross-domain separation path computation request, acquiring K pairs of candidate separation domain sequences according to a cross-domain network abstraction topology; traversing the K pairs of sequences, generating corresponding intra-domain path computation requests for various domains through which candidate separation domain sequences in the network pass to transmit; when receiving at least one pair of intra-domain paths for the request, configuring each of the at least one pair of intra-domain paths to a corresponding position in the K pairs of sequences, to form K pairs of candidate cross-domain separation paths; and determining one pair of cross-domain separation paths from the K pairs of paths as a computation result of the cross-domain separation path computation request to transmit. There are also disclosed another method for acquiring a cross-domain separation path, a path computation element, and a computer storage medium.

TECHNICAL FIELD

The present disclosure relates to a path acquisition method, and inparticular, to a method for acquiring a cross-domain separation path, arelated Path Computation Element (PCE), and a related computer storagemedium.

BACKGROUND OF THE RELATED ART

In a cross-domain MultiProtocol Label Switching Traffic Engineering(MPLS-TE) and Generalized MultiProtocol Label Switching (GMPLS) network,due to requirements for management, geographic positions, and switchingenvironments, the network may be divided into multiple domains and onedomain is connected to another domain through a link between boundarynodes which egress and ingress the domains. This link connection iscommonly referred to as a Label Switching Path (LSP) in a multi-domainnetwork environment.

In the multi-domain network environment, two LSPs are usually configuredfor each bearer service. One LSP is called a working path and the otherLSP is called a protection path (backup path), in case when the workingpath fails, the protection path is used for transmission of services. Onthe basis of this, the protection path configured for the working pathis a path having the same source node and destination node as those onthe working path, but having other nodes, links and Share Risk LinkGroup (SRLGs) etc. which are completely separated (different) from thoseof the working path.

For the cross-domain separation (disjoint) path computation method, theInternet communication protocol standard RFC5298 proposes two basicmethods, one is sequential path computation and the other issimultaneous path computation. Herein, as a working path is computedprior to a protection path in the sequential path computation, nodes andlinks of a working path in each domain have been determined before aprotection path is computed. At the same time, the protection path to becomputed needs to satisfy a constraint condition that its respectivenodes, links, and SRLGs are all separated from those of the workingpath. When there are some limitations, for example, nodes or linksselected for the working path which is computed firstly areunreasonable, it will lead to a failure in computing a protection pathwhich is separated from the nodes, links and SRLGs of the working pathin a domain, thereby resulting in a failure in the cross-domainseparation path computation. For the simultaneous path computation, asuccess ratio of the sequential path computation for acquisition of across-domain separation path is theoretically increased, but a domainsequence between a head domain and a tail domain of a cross-domainend-to-end path needs to be known in advance before this method is used.

SUMMARY

In order to solve the existing technical problem, the embodiments of thepresent disclosure aim to provide a method for acquiring a cross-domainseparation path, a related path computation element and a computerstorage medium, which can improve a success ratio of acquisition of across-domain separation path, and a domain sequence between a headdomain and a tail domain of an end-to-end path needs not to be known inadvance.

Technical solutions of the embodiments of the present disclosure areachieved as follows.

An embodiment of the present disclosure provides a method for acquiringa cross-domain separation path, including:

when a cross-domain separation path computation request is received,acquiring K pairs of candidate separation domain sequences according toa cross-domain network abstraction topology;

traversing the K pairs of candidate separation domain sequences,generating corresponding intra-domain path computation requests forvarious domains through which candidate separation domain sequences inthe network pass, and transmitting the intra-domain path computationrequests of the various domains;

when at least one pair of intra-domain paths for the intra-domain pathcomputation request are received, configuring each intra-domain path ofthe at least one pair of intra-domain paths to a corresponding positionin the K pairs of candidate separation domain sequences, to form K pairsof candidate cross-domain separation paths;

determining one pair of cross-domain separation paths from the K pairsof candidate cross-domain separation paths, and

transmitting the cross-domain separation paths as a computation resultof the cross-domain separation path computation request;

where K is a positive integer.

In the above solution, acquiring the K pairs of candidate separationdomain sequences according to the cross-domain network abstractiontopology includes:

initializing K, initializing a positive integer j to be 1, and computinga working path domain sequence in a first pair of candidate separationdomain sequences from the K pairs of candidate separation domainsequences from a head node to a tail node of the network using a presetshortest path algorithm according to an inter-domain topology consistedof ingress and egress boundary nodes and inter-domain links of variousdomains; herein the head node and the tail node are carried in thecross-domain separation path computation request;

computing a protection path domain sequence in the first pair ofcandidate separation domain sequences using the shortest path algorithmby taking pass-through paths of the working path domain sequence in thefirst pair of candidate separation domain sequences as a separationconstraint condition;

adding 1 to j, judging whether j+1 is greater than the positive integerK, and when it is judged that j+1 is not greater than K, computing aworking path domain sequence in a second pair of candidate separationdomain sequences which is sub-optimal relative to the working pathdomain sequence in the first pair of candidate separation domainsequences using a preset K-optimal path algorithm;

computing a protection path domain sequence in the second pair ofcandidate separation domain sequences using the shortest path algorithmby taking pass-through paths of the working path domain sequence in thesecond pair of candidate separation domain sequences as a separationconstraint condition;

adding 1 to j again, judging whether j+1 is greater than the positiveinteger K, and when it is judged that j+1 is not greater than K,computing a working path domain sequence in a third pair of candidateseparation domain sequences which is sub-optimal relative to the workingpath domain sequence in the second pair of candidate separation domainsequences using the preset K-optimal path algorithm;

computing a protection path domain sequence in the third pair ofcandidate separation domain sequences using the shortest path algorithmby taking pass-through paths of the working path domain sequence in thethird pair of candidate separation domain sequences as a separationconstraint condition;

and so on, until it is judged that j+1 is greater than K, and theprocess ends.

In the above solution, traversing the K pairs of candidate separationdomain sequences, and generating corresponding intra-domain pathcomputation requests for various domains in the network includes:

for a head domain of the various domains, generating an associated pathcomputation request each time a pair of candidate separation domainsequences in the K pairs of candidate separation domain sequences istraversed; acquiring an associated path computation request generatedfor a j1^(th) pair of candidate sequences, and determining theassociated path computation request as a first association request;acquiring an associated path computation request generated for a j2^(th)pair of candidate sequences, and determining the associated pathcomputation request as a second association request; and in the K pairsof candidate separation domain sequences, there is an egress boundarynode of a working path domain sequence in the j1^(th) pair of candidatesequences in the head domain which is the same as an egress boundarynode of a working path domain sequence in the j2^(th) pair of candidatesequences in the head domain, and when an egress boundary node of aprotection path domain sequence in the j1^(th) pair of candidatesequences in the head domain is the same as an egress boundary node of aprotection path domain sequence in the j2^(th) pair of candidatesequences in the head domain, merging the first association request andthe second association request into an associated path computationrequest, and using the merged associated path computation request as anintra-domain path computation request of the head domain;

for a tail domain of the various domains, generating an associated pathcomputation request each time a pair of candidate separation domainsequences in the K pairs of candidate separation domain sequences istraversed; acquiring an associated path computation request generatedfor a j1^(th) pair of candidate sequences, and determining theassociated path computation request as a first association request;acquiring an associated path computation request generated for a j2^(th)pair of candidate sequences, and determining the associated pathcomputation request as a second association request; and in the K pairsof candidate separation domain sequences, there is an ingress boundarynode of a working path domain sequence in the j1^(th) pair of candidatesequences in the tail domain which is the same as an ingress boundarynode of a working path domain sequence in the j2^(th) pair of candidatesequences in the tail domain, and when an ingress boundary node of aprotection path domain sequence in the j1^(th) pair of candidatesequences in the tail domain is the same as an ingress boundary node ofa protection path domain sequence in the j2^(th) pair of candidatesequences in the tail domain, merging the first association request andthe second association request into an associated path computationrequest, and using the merged associated path computation request as anintra-domain path computation request of the tail domain;

for an intermediate domain of the various domains, when a working pathdomain sequence and a protection path domain sequence in a j^(th) pairof candidate separation domain sequences in the K pairs of candidateseparation domain sequences pass through the intermediate domain,traversing the j^(th) pair of candidate separation domain sequences andgenerating an associated path computation request for the j^(th) pair ofcandidate separation domain sequences; acquiring an associated pathcomputation request generated for a j1^(th) pair of candidate sequences,and determining the associated path computation request as a firstassociation request; acquiring an associated path computation requestgenerated for a j2^(th) pair of candidate sequences, and determining theassociated path computation request as a second association request; andin at least two pairs of candidate separation domain sequences in whicha working path domain sequences and a protection path domain sequencepass through the intermediate domain, there are ingress and egressboundary nodes of a working path domain sequence in the j1^(th) pair ofcandidate sequences in the intermediate domain which are correspondinglythe same as ingress and egress boundary nodes of a working path domainsequence in the j2^(th) pair of candidate sequences in the intermediatedomain, and when ingress and egress boundary nodes of a protection pathdomain sequence in the j1^(th) pair of candidate sequences in theintermediate domain are correspondingly the same as ingress and egressboundary nodes of a protection path domain sequence in the j2^(th) pairof candidate sequences in the intermediate domain, merging the firstassociation request and the second association request into anassociated path computation request, and using the merged associatedpath computation request as an intra-domain path computation request ofthe intermediate domain; and

for an intermediate domain of the various domains, when only one of aworking path domain sequence and a protection path domain sequence inthe j^(th) pair of candidate separation domain sequences in the K pairsof candidate separation domain sequences passes through the intermediatedomain, generating a non-associated path computation request for adomain sequence which passes through the intermediate domain; acquiringa non-associated path computation request generated for a working pathdomain sequence or a protection path domain sequence of a j1^(th) pairof candidate sequences, and determining the non-associated pathcomputation request as a first non-association request; acquiring anon-associated path computation request generated for a working pathdomain sequence or a protection path domain sequence of a j2^(th) pairof candidate sequences, and determining the non-associated pathcomputation request as a second non-association request; and wheningress and egress domain boundary nodes of a domain sequencecorresponding to the first non-associated path computation request inthe intermediate domain are the same as ingress and egress domainboundary nodes of a domain sequence corresponding to the secondnon-associated path computation request in the intermediate domain,merging the first non-association request and the second non-associationrequest, and using the merged non-associated path computation request asan intra-domain path computation request of the intermediate domain;

herein, j, j1 and j2 are positive integers, 1≤j≤K, 1≤j1≤K, 1≤j2≤K andj1≠j2.

In the above solution, configuring each intra-domain path of the atleast one pair of intra-domain paths to a corresponding position in theK pairs of candidate separation domain sequences, to form K pairs ofcandidate cross-domain separation paths includes:

in the K pairs of candidate separation domain sequences, configuringintra-domain paths in pass-through domains corresponding to a workingpath domain sequence in a j^(th) pair of candidate separation domainsequences to corresponding positions of a working path in the j^(th)pair of candidate separation domain sequences, and configuringintra-domain paths in pass-through domains corresponding to a protectionpath domain sequence in the j^(th) pair of candidate separation domainsequences to corresponding positions of a protection path in the j^(th)pair of candidate separation domain sequences, to form the K pairs ofcandidate cross-domain separation paths;

herein j is a positive integer and 1≤j≤K.

In the above solution, determining one pair of cross-domain separationpaths from the K pairs of candidate cross-domain separation pathsincludes:

computing a path cost of a working path and a path cost of a protectionpath in each of the K pairs of candidate cross-domain separation paths;

summing the path cost of the working path and the path cost of theprotection path in each pair of candidate cross-domain separation pathsto form a path cost sum; and

selecting candidate cross-domain separation paths with a minimum pathcost sum as the cross-domain separation paths.

An embodiment of the present disclosure further provides a method foracquiring a cross-domain separation path, including:

when a cross-domain separation path computation request of a node isreceived, one of at least one sub-Path Computation Element (PCE) whichis used to administer a domain to which the node belongs transmittingthe cross-domain separation path computation request;

each of the at least one sub-PCE determining a type of an intra-domainpath computation request received by the sub-PCE itself, acquiring atleast one pair of intra-domain paths in a domain administered by thesub-PCE itself according to the type and domain boundary nodes carriedin the intra-domain path computation request, and transmitting theacquired intra-domain paths; and

receiving a cross-domain separation path computation result for thecross-domain separation path computation request and transmitting thereceived cross-domain separation path computation result to the node.

In the above solution, each of the at least one sub-PCE determining atype of the intra-domain path computation request received by thesub-PCE itself, acquiring at least one pair of intra-domain paths in adomain to which the sub-PCE itself belongs according to the type and thedomain boundary nodes carried in the intra-domain path computationrequest includes:

when a type of an intra-domain path computation request received by asub-PCE which is used to compute intra-domain paths in a head domain isan associated path computation request, computing intra-domain paths inthe head domain for each associated path computation request accordingto an egress boundary node of the head domain carried in the associatedpath computation request using a preset simultaneous disjoint pathalgorithm;

when a type of an intra-domain path computation request received by asub-PCE which is used to compute intra-domain paths in a tail domain isan associated path computation request, computing intra-domain paths inthe tail domain for each associated path computation request accordingto an ingress boundary node of the tail domain carried in the associatedpath computation request using the preset simultaneous disjoint pathalgorithm; and

when a type of an intra-domain path computation request received by asub-PCE which is used to compute intra-domain paths in an intermediatedomain includes an associated path computation request and anon-associated path computation request, for the associated pathcomputation request, computing disjoint working path and protection pathcorresponding to the working path in the intermediate domain for eachassociation request according to ingress and egress boundary nodes ofthe intermediate domain carried in the associated path computationrequest using the preset simultaneous disjoint path algorithm, andaggregating the working path and the protection path as the intra-domainpaths; and for the non-associated path computation request, computing asingle path in the intermediate domain according to ingress and egressboundary nodes of the intermediate domain carried in the non-associationrequest using a preset shortest path algorithm and/or a K-optimal pathalgorithm, and using the single path as the intra-domain path.

In the above solution, the method further includes:

when the sub-PCE which is used to compute the intra-domain paths in thehead domain receives the associated path computation request, newlyadding a virtual node in an intra-domain topology of the head domain andnewly adding virtual links through which the virtual node is connectedto first and second egress boundary nodes;

forming an intra-domain path computation topology of the head domainaccording to the virtual node and the virtual links;

in the intra-domain path computation topology of the head domain,computing a pair of shortest disjoint paths from a head node to thevirtual node in the head domain using the preset simultaneous disjointpath algorithm;

separating a path from the head node to the first egress boundary nodeof the head domain from the pair of shortest disjoint paths to form anintra-domain working path;

separating a path from the head node to the second egress boundary nodeof the head domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

using the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the head domain;

herein, the first egress boundary node is an egress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the head domain; and

the second egress boundary node is an egress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the head domain,

where K and j are positive integers, and 1≤j≤K.

In the above solution, the method further includes:

when the sub-PCE which is used to compute the intra-domain paths in thetail domain receives the associated path computation request, newlyadding a virtual node in an intra-domain topology of the tail domain andnewly adding virtual links through which the virtual node is connectedto first and second ingress boundary nodes;

forming an intra-domain path computation topology of the tail domainaccording to the virtual node and the virtual links;

in the intra-domain path computation topology of the tail domain,computing a pair of shortest disjoint paths from the virtual node to atail node in the tail domain using the preset simultaneous disjoint pathalgorithm;

separating a path from the first ingress boundary node to the tail nodein the tail domain from the pair of shortest disjoint paths to form anintra-domain working path;

separating a path from the second ingress boundary node to the tail nodein the tail domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

using the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the tail domain;

herein, the first ingress boundary node is an ingress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the tail domain; and

the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the tail domain,

where K and j are positive integers, and 1≤j≤K.

In the above solution, the method further includes:

when the sub-PCE which is used to compute the intra-domain paths in theintermediate domain receives the associated path computation request,newly adding a first virtual node and a second virtual node in anintra-domain topology of the tail domain and newly adding virtual linksthrough which the first virtual node is connected to first and secondingress boundary nodes and virtual links through which the secondvirtual node is connected to first and second egress boundary nodes;

forming an intra-domain path computation topology of the intermediatedomain according to the first virtual node, the second virtual node andthe virtual links;

in the intra-domain path computation topology of the intermediatedomain, computing a pair of shortest disjoint paths from the firstvirtual node to the second virtual node using the preset simultaneousdisjoint path algorithm;

separating a path from the first ingress boundary node of theintermediate domain to the first egress boundary node of theintermediate domain from the pair of shortest disjoint paths to form anintra-domain working path;

separating a path from the second ingress boundary node of theintermediate domain to the second egress boundary node of theintermediate domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

using the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the intermediate domain;

herein, the first ingress boundary node is an ingress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the intermediate domain, and the first egressboundary node is an egress boundary node of the working path domainsequence in the intermediate domain; and

the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the intermediate domain, andthe second egress boundary node is an egress boundary node of theprotection path domain sequence in the intermediate domain;

where K and j are positive integers, and 1≤j≤K.

An embodiment of the present disclosure further provides a pathcomputation element, including:

a first acquisition unit arranged to: when a cross-domain separationpath computation request is received, acquire K pairs of candidateseparation domain sequences according to a cross-domain networkabstraction topology;

a first generation unit arranged to traverse the K pairs of candidateseparation domain sequences, generate corresponding intra-domain pathcomputation requests for various domains through which candidateseparation domain sequences in the network pass, and transmit theintra-domain path computation requests of the various domains;

a first formation unit arranged to when at least one pair ofintra-domain paths for the intra-domain path computation request arereceived, arrange each intra-domain path of the at least one pair ofintra-domain paths to a corresponding position in the K pairs ofcandidate separation domain sequences, to form K pairs of candidatecross-domain separation paths;

a first determination unit arranged to determine one pair ofcross-domain separation paths from the K pairs of candidate cross-domainseparation paths, and

a first transmission unit arranged to transmit the cross-domainseparation paths as a computation result of the cross-domain separationpath computation request;

herein K is a positive integer.

In the above solution, the first acquisition unit is arranged to:

initialize K, initialize a positive integer j to be 1, and compute aworking path domain sequence in a first pair of candidate separationdomain sequences from the K pairs of candidate separation domainsequences from a head node to a tail node of the network using a presetshortest path algorithm according to an inter-domain topology consistedof ingress and egress boundary nodes and inter-domain links of variousdomains; herein the head node and the tail node are carried in thecross-domain separation path computation request;

compute a protection path domain sequence in the first pair of candidateseparation domain sequences using the shortest path algorithm by takingpass-through paths of the working path domain sequence in the first pairof candidate separation domain sequences as a separation constraintcondition;

add 1 to j, judge whether j+1 is greater than the positive integer K,and when it is judged that j+1 is not greater than K, compute a workingpath domain sequence in a second pair of candidate separation domainsequences which is sub-optimal relative to the working path domainsequence in the first pair of candidate separation domain sequencesusing a preset K-optimal path algorithm;

compute a protection path domain sequence in the second pair ofcandidate separation domain sequences using the shortest path algorithmby taking pass-through paths of the working path domain sequence in thesecond pair of candidate separation domain sequences as a separationconstraint condition;

add 1 to j again, judge whether j+1 is greater than the positive integerK, and when it is judged that j+1 is not greater than K, compute aworking path domain sequence in a third pair of candidate separationdomain sequences which is sub-optimal relative to the working pathdomain sequence in the second pair of candidate separation domainsequences using the preset K-optimal path algorithm;

compute a protection path domain sequence in the third pair of candidateseparation domain sequences using the shortest path algorithm by takingpass-through paths of the working path domain sequence in the third pairof candidate separation domain sequences as a separation constraintcondition;

and so on, until it is judged that j+1 is greater than K.

In the above solution, the first generation unit is arranged to:

for a head domain of the various domains, generate an associated pathcomputation request each time a pair of candidate separation domainsequences in the K pairs of candidate separation domain sequences istraversed; acquire an associated path computation request generated fora j1^(th) pair of candidate sequences, and determine the associated pathcomputation request as a first association request; acquire anassociated path computation request generated for a j2^(th) pair ofcandidate sequences, and determine the associated path computationrequest as a second association request; and in the K pairs of candidateseparation domain sequences, there is an egress boundary node of aworking path domain sequence in the j1^(th) pair of candidate sequencesin the head domain which is the same as an egress boundary node of aworking path domain sequence in the j2^(th) pair of candidate sequencesin the head domain, and when an egress boundary node of a protectionpath domain sequence in the j1^(th) pair of candidate sequences in thehead domain is the same as an egress boundary node of a protection pathdomain sequence in the j2^(th) pair of candidate sequences in the headdomain, merge the first association request and the second associationrequest into an associated path computation request, and use the mergedassociated path computation request as an intra-domain path computationrequest of the head domain;

for a tail domain of the various domains, generate an associated pathcomputation request each time a pair of candidate separation domainsequences in the K pairs of candidate separation domain sequences istraversed; acquire an associated path computation request generated fora j1^(th) pair of candidate sequences, and determine the associated pathcomputation request as a first association request; acquire anassociated path computation request generated for a j2^(th) pair ofcandidate sequences, and determine the associated path computationrequest as a second association request; and in the K pairs of candidateseparation domain sequences, there is an ingress boundary node of aworking path domain sequence in the j1^(th) pair of candidate sequencesin the tail domain which is the same as an ingress boundary node of aworking path domain sequence in the j2^(th) pair of candidate sequencesin the tail domain, and when an ingress boundary node of a protectionpath domain sequence in the j1^(th) pair of candidate sequences in thetail domain is the same as an ingress boundary node of a protection pathdomain sequence in the j2^(th) pair of candidate sequences in the taildomain, merge the first association request and the second associationrequest into an associated path computation request, and use the mergedassociated path computation request as an intra-domain path computationrequest of the tail domain;

for an intermediate domain of the various domains, when a working pathdomain sequence and a protection path domain sequence in a j^(th) pairof candidate separation domain sequences in the K pairs of candidateseparation domain sequences pass through the intermediate domain,traverse the j^(th) pair of candidate separation domain sequences andgenerate an associated path computation request for the j^(th) pair ofcandidate separation domain sequences; acquire an associated pathcomputation request generated for a j1^(th) pair of candidate sequences,and determine the associated path computation request as a firstassociation request; acquire an associated path computation requestgenerated for a j2^(th) pair of candidate sequences, and determine theassociated path computation request as a second association request; andin at least two pairs of candidate separation domain sequences in whicha working path domain sequences and a protection path domain sequencepass through the intermediate domain, there are ingress and egressboundary nodes of a working path domain sequence in the j1^(th) pair ofcandidate sequences in the intermediate domain which are correspondinglythe same as ingress and egress boundary nodes of a working path domainsequence in the j2^(th) pair of candidate sequences in the intermediatedomain, and when ingress and egress boundary nodes of a protection pathdomain sequence in the j1^(th) pair of candidate sequences in theintermediate domain are correspondingly the same as ingress and egressboundary nodes of a protection path domain sequence in the j2^(th) pairof candidate sequences in the intermediate domain, merge the firstassociation request and the second association request into anassociated path computation request, and use the merged associated pathcomputation request as an intra-domain path computation request of theintermediate domain; and

for an intermediate domain of the various domains, when only one of aworking path domain sequence and a protection path domain sequence inthe j^(th) pair of candidate separation domain sequences in the K pairsof candidate separation domain sequences passes through the intermediatedomain, generate a non-associated path computation request for a domainsequence which passes through the intermediate domain; acquire anon-associated path computation request generated for a working pathdomain sequence or a protection path domain sequence of a j1^(th) pairof candidate sequences, and determine the non-associated pathcomputation request as a first non-association request; acquire anon-associated path computation request generated for a working pathdomain sequence or a protection path domain sequence of a j2^(th) pairof candidate sequences, and determine the non-associated pathcomputation request as a second non-association request; and wheningress and egress boundary nodes of a domain sequence corresponding tothe first non-associated path computation request in the intermediatedomain are the same as ingress and egress boundary nodes of a domainsequence corresponding to the second non-associated path computationrequest in the intermediate domain, merge the first non-associationrequest and the second non-association request, and use the mergednon-associated path computation request as an intra-domain pathcomputation request of the intermediate domain;

where, j, j1 and j2 are positive integers, 1≤j≤K, 1≤j1≤K, 1≤j2≤K andj1≠j2

In the above solution, the first formation unit is arranged to:

in the K pairs of candidate separation domain sequences, configureintra-domain paths in pass-through domains corresponding to a workingpath domain sequence in a j^(th) pair of candidate separation domainsequences to corresponding positions of a working path in the j^(th)pair of candidate separation domain sequences, and configureintra-domain paths in pass-through domains corresponding to a protectionpath domain sequence in the j^(th) pair of candidate separation domainsequences to corresponding positions of a protection path in the j^(th)pair of candidate separation domain sequences, to form the K pairs ofcandidate cross-domain separation paths;

where j is a positive integer and 1≤j≤K.

In the above solution, the first determination unit is arranged to:

compute a path cost of a working path and a path cost of a protectionpath in each of the K pairs of candidate cross-domain separation paths;

sum the path cost of the working path and the path cost of theprotection path in each pair of candidate cross-domain separation pathsto form a path cost sum; and

select candidate cross-domain separation paths with a minimum path costsum as the cross-domain separation paths.

An embodiment of the present disclosure further provides a pathcomputation element, including:

a first transmission unit arranged to, when a cross-domain separationpath computation request of a node is received, transmit thecross-domain separation path computation request;

a first determination unit arranged to determine a type of anintra-domain path computation request received by itself;

a first acquisition unit arranged to acquire at least one pair ofintra-domain paths in a domain administered by itself according to thetype and domain boundary nodes carried in the intra-domain pathcomputation request, and transmit the acquired intra-domain paths; and

a second transmission unit arranged to receive a cross-domain separationpath computation result for the cross-domain separation path computationrequest and transmit the received cross-domain separation pathcomputation result to the node.

In the above solution,

the first acquisition unit is located in a head domain, and is arrangedto when determining that a type of an intra-domain path computationrequest received by itself is an associated path computation request,compute intra-domain paths in the head domain for each associated pathcomputation request according to an egress boundary node of the headdomain carried in the associated path computation request using a presetsimultaneous disjoint path algorithm;

the first acquisition unit is located in a tail domain, and is arrangedto when determining that a type of a received intra-domain pathcomputation request is an associated path computation request, computeintra-domain paths in the tail domain for each associated pathcomputation request according to an ingress boundary node of the taildomain carried in the associated path computation request using thepreset simultaneous disjoint path algorithm; and

the first acquisition unit is located in an intermediate domain and isarranged to when determining that a type of a received intra-domain pathcomputation request includes an associated path computation request anda non-associated path computation request, for the associated pathcomputation request, compute disjoint working path and protection pathcorresponding to the working path in the intermediate domain for eachassociation request according to ingress and egress boundary nodes ofthe intermediate domain carried in the associated path computationrequest using the preset simultaneous disjoint path algorithm, andaggregate the working path and the protection path as the intra-domainpaths; and for the non-associated path computation request, compute asingle path in the intermediate domain according to ingress and egressboundary nodes of the intermediate domain carried in the non-associationrequest using a preset shortest path algorithm and/or a K-optimal pathalgorithm, and use the single path as the intra-domain path.

In the above solution,

the first acquisition unit is located in the head domain, and isarranged to, when it is determined that the associated path computationrequest is received, newly add a virtual node in an intra-domaintopology of the head domain and newly add virtual links through whichthe virtual node is connected to first and second egress boundary nodes;

form an intra-domain path computation topology of the head domainaccording to the virtual node and the virtual links;

in the intra-domain path computation topology of the head domain,compute a pair of shortest disjoint paths from a head node to thevirtual node in the head domain using the preset simultaneous disjointpath algorithm;

separate a path from the head node to the first egress boundary node ofthe head domain from the pair of shortest disjoint paths to form anintra-domain working path;

separate a path from the head node to the second egress boundary node ofthe head domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

use the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the head domain;

herein, the first egress boundary node is an egress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the head domain; and

the second egress boundary node is an egress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the head domain,

where K and j are positive integers, and 1≤j≤K.

In the above solution,

the first acquisition unit is located in the tail domain and is arrangedto when it is determined that the associated path computation request isreceived, newly add a virtual node in an intra-domain topology of thetail domain and newly add virtual links through which the virtual nodeis connected to first and second ingress boundary nodes;

form an intra-domain path computation topology of the tail domainaccording to the virtual node and the virtual links;

in the intra-domain path computation topology of the tail domain,compute a pair of shortest disjoint paths from the virtual node to atail node in the tail domain using the preset simultaneous disjoint pathalgorithm;

separate a path from the first ingress boundary node to the tail node inthe tail domain from the pair of shortest disjoint paths to form anintra-domain working path;

separate a path from the second ingress boundary node to the tail nodein the tail domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

use the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the tail domain;

herein, the first ingress boundary node is an ingress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the tail domain; and

the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the tail domain, where K andj are positive integers, and 1≤j≤K.

In the above solution,

the first acquisition unit is located in the intermediate domain and isarranged to, when the associated path computation request is received,newly add a first virtual node and a second virtual node in anintra-domain topology of the tail domain and newly add virtual linksthrough which the first virtual node is connected to first and secondingress boundary nodes and virtual links through which the secondvirtual node is connected to first and second egress boundary nodes;

form an intra-domain path computation topology of the intermediatedomain according to the first virtual node, the second virtual node andthe virtual links;

in the intra-domain path computation topology of the intermediatedomain, compute a pair of shortest disjoint paths from the first virtualnode to the second virtual node using the preset simultaneous disjointpath algorithm;

separate a path from the first ingress boundary node of the intermediatedomain to the first egress boundary node of the intermediate domain fromthe pair of shortest disjoint paths to form an intra-domain workingpath;

separate a path from the second ingress boundary node of theintermediate domain to the second egress boundary node of theintermediate domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

use the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the intermediate domain;

herein, the first ingress boundary node is an ingress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the intermediate domain, and the first egressboundary node is an egress boundary node of the working path domainsequence in the intermediate domain; and

the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the intermediate domain, andthe second egress boundary node is an egress boundary node of theprotection path domain sequence in the intermediate domain;

where K and j are positive integers, and 1≤j≤K.

An embodiment of the present disclosure further provides a computerstorage medium having a first set of computer-executable instructionsstored therein, which is used to perform the first method for acquiringa cross-domain separation path described above.

An embodiment of the present disclosure further provides a secondcomputer storage medium having a second set of computer-executableinstructions stored therein, which is used to perform the second methodfor acquiring a cross-domain separation path described above.

The method for acquiring a cross-domain separation path, the relatedpath computation element, and the related computer storage medium aredisclosed according to the embodiments of the present disclosure,herein, the method includes: when a cross-domain separation pathcomputation request is received, acquiring K pairs of candidateseparation domain sequences according to a cross-domain networkabstraction topology; traversing the K pairs of candidate separationdomain sequences, generating corresponding intra-domain path computationrequests for domains through which various candidate separation domainsequences in the network pass, and transmitting the intra-domain pathcomputation requests of the various domains; when at least one pair ofintra-domain paths for the intra-domain path computation request arereceived, configuring each intra-domain path of the at least one pair ofintra-domain paths to a corresponding position in the K pairs ofcandidate separation domain sequences, to form K pairs of candidatecross-domain separation paths; determining one pair of cross-domainseparation paths from the K pairs of candidate cross-domain separationpaths, and transmitting the cross-domain separation paths as acomputation result of the cross-domain separation path computationrequest; where K is a positive integer. With the embodiments of thepresent disclosure, a success ratio of acquisition of a cross-domainseparation path can be increased, and a domain sequence between a headdomain and a tail domain of an end-to-end path needs not to be known inadvance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart of an implementation of embodiment one of a methodfor acquiring a cross-domain separation path according to the presentdisclosure;

FIG. 2 is a diagram of application scenario one according to anembodiment of the present disclosure;

FIG. 3(a) is a topological diagram of a head domain according to anembodiment of the present disclosure;

FIG. 3(b) is a topological diagram of a tail domain according to anembodiment of the present disclosure;

FIG. 3(c) is a topological diagram of an intermediate domain accordingto an embodiment of the present disclosure;

FIG. 4 is a flowchart of implementation two of a method for acquiring across-domain separation path according to the present disclosure;

FIG. 5 is a flowchart of implementation three of a method for acquiringa cross-domain separation path according to the present disclosure;

FIG. 6 is a diagram of embodiment one of a method for acquiring across-domain separation path according to the present disclosure;

FIG. 7 is a diagram of embodiment two of a method for acquiring across-domain separation path according to the present disclosure;

FIG. 8 is a diagram of embodiment three of a method for acquiring across-domain separation path according to the present disclosure;

FIG. 9 is a constitutional diagram of embodiment one of a pathcomputation element according to the present disclosure; and

FIG. 10 is a constitutional diagram of embodiment two of a pathcomputation element according to the present disclosure.

SPECIFIC EMBODIMENTS

Optional embodiments of the present disclosure will be described indetail below with reference to accompanying drawings, and it is to beunderstood that the optional embodiments described hereinafter aremerely for the purpose of illustration and explanation of the presentdisclosure and are not intended to limit the present disclosure.

In a multi-domain network environment, in order to meet the requirementsfor establishment of a working path and a protection path, PCEs may beused to establish an LSP. When PCEs are used to compute a cross-domainseparation path, PCEs which are responsible for computing various domainpaths are required to cooperate with each other to complete thecomputation of an end-to-end path. In order to solve the problem thatthe cross-domain separation path can be established without knowing inadvance a domain sequence between a head domain and a tail domain of across-domain end-to-end path, on the basis of the current PCEarchitecture, the Internet communication protocol standard RFC6805proposes a hierarchical PCE concept, that is, PCEs which are responsiblefor computation of intra-domain paths in various domains are consideredto be sub-PCEs, a parent PCE is set for these PCEs, and the computationof the cross-domain separation path is completed by coordinating thesub-PCEs in various domains by the parent PCE. The subsequent technicalsolution according to the embodiments of the present disclosure is toacquire the cross-domain separation path using the hierarchical PCEconceptual model.

Embodiment one of a method for acquiring a cross-domain separation pathaccording to the present disclosure is applied in PCEs. The PCEs includea parent PCE and at least one sub-PCE. Each sub-PCE corresponds to acorresponding domain in the network.

FIG. 1 is a flowchart of implementation one of a method for acquiring across-domain separation path according to the present disclosure. Asshown in FIG. 1, the method includes the following steps:

In step 11, when a cross-domain separation path computation requesttransmitted by a node is received, one of the at least one sub-PCE whichis used to administer a domain to which the node belongs transmits thecomputation request to the parent PCE.

FIG. 2 is a diagram of application scenario one according to anembodiment of the present disclosure. The technical solution ofembodiment one of the method for acquiring a cross-domain separationpath according to the present disclosure can be understood incombination with FIG. 2.

As shown in FIG. 2, there are n (n is a positive integer) domains in thenetwork, and each domain is a corresponding Autonomous System (AS), thatis, a domain in the network is AS(i), wherein i is a positive integerand 1<=i<=n.

For convenience of understanding, in the cross-domain separation pathcomputation, AS(1) may be considered to be a head domain, AS(n) may beconsidered to be a tail domain, and AS(2)-AS(n−1) may be considered tobe intermediate domains. In a hierarchical PCE conceptual model, acorresponding sub-PCE such as PCE_S(i) is configured for AS(i), and aparent PCE such as PCE_P is configured for all the sub-PCEs in thenetwork.

In an embodiment, when a node S transmits a cross-domain separation pathcomputation request to a sub-PCE which is used to administer the node Ssuch as PCE_S(1), the PCE_S(1) transmits the cross-domain separationpath computation request to the PCE_P.

In step 12, when the parent PCE receives the computation request, Kpairs of candidate separation domain sequences are acquired according toa cross-domain network abstraction topology; and the K pairs ofcandidate separation domain sequences are traversed, correspondingintra-domain path computation requests are generated for domains throughwhich each candidate separation domain sequence in the network passes,and an intra-domain path computation request of each domain istransmitted to a sub-PCE corresponding to the domain.

Herein, the pass-through domains include: a head domain, a tail domain,and intermediate domains through which the candidate separation domainsequence passes in the cross-domain network; and each of the K pairs ofcandidate separation domain sequences includes a domain sequence of aworking path in candidate cross-domain separation paths and a domainsequence of a protection path corresponding to the working path in thecandidate cross-domain separation paths.

Herein, K is a positive integer, which is preset and can be set flexiblyaccording to an actual network topological structure and/or the pathcomputation method which is used.

Here, the following parameters are appointed in combination with FIG. 2for convenience of description of the technical solution according tothe embodiments of the present disclosure.

DS(og, j) represents a pass-through domain sequence of a working path ina j^(th) pair of candidate separation domain sequences, herein 1<=j<=K;

DS(dj, j) represents a pass-through domain sequence of a protection pathin the j^(th) pair of candidate separation domain sequences, herein j isa positive integer and 1<=j<=K;

BN-en(og, i, j) represents an ingress boundary node used for a workingpath which passes through the domain AS(i) in the j^(th) pair ofcandidate separation domain sequences;

BN-ex(og, i, j) represents an egress boundary node used for the workingpath which passes through the domain AS(i) in the j^(th) pair ofcandidate separation domain sequences;

BN-en(dj, i, j) represents an ingress boundary node used for aprotection path which passes through the domain AS(i) in the j^(th) pairof candidate separation domain sequences;

BN-ex(dj, i, j) represents an egress boundary node used for the workingpath which passes through the domain AS(i) in the j^(th) pair ofcandidate separation domain sequences;

Pin(og, i, j) represents an intra-domain path of the working path whichpasses through the domain AS(i) in the j^(th) pair of candidateseparation domain sequences;

PKey(og, i, j) represents a PathKey used for an intra-domain pathsegment of the working path which passes through the domain AS(i) in thej^(th) pair of candidate separation domain sequences;

Pin(dj, i, j) represents an intra-domain path of the protection pathwhich passes through the domain AS(i) in the j^(th) pair of candidateseparation domain sequences;

PKey(dj, i, j) represents a PathKey used for an intra-domain pathsegment of the protection path which passes through the domain AS(i) inthe j^(th) pair of candidate separation domain sequences;

S represents a head/source node of the cross-domain separation pathcomputation and is located in the head domain AS(1);

D represents a tail node of the cross-domain separation pathcomputation, and is located in the tail domain AS(n);

other domains except the head domain AS(1) and the tail domain AS(n) arecalled intermediate domains;

SUB_REQ(i) represents an intra-domain (disjoint) path computationrequest transmitted by the parent PCE to the sub-PCE(i) responsible forcomputing the intra-domain(disjoint) path of the domain AS(i);

SUB_RSP(i) represents a set of intra-domain path computation results ofthe domain AS(i) transmitted by the PCE_S(i) to the PCE_P;

DP(og, j) represents a cross-domain end-to-end path corresponding to theworking path in the j^(th) pair of candidate separation domainsequences;

DP(dj, j) represents a cross-domain end-to-end path corresponding to theprotection path in the j^(th) pair of candidate separation domainsequences.

Herein, when receiving the computation request, the parent PCE acquiringK pairs of candidate separation domain sequences according to across-domain network abstraction topology includes:

the parent PCE, such as the PCE_P, computing the K pairs of candidateseparation domain sequences in accordance with step 121 to step 124using the sequential path computation according to an inter-domaintopology consisted of ingress and egress boundary nodes and inter-domainlinks of various domains.

In step 121, K is initialized, j is initialized to be equal to 1, andthe PCE_P computes a pass-through domain sequence DS(o, j) of a workingpath in a first pair of candidate cross-domain separation paths from ahead node S to a tail node D using a preset shortest path algorithm, andthe process continues to perform step 122.

Herein, a specific path (a working path in the first pair of candidatecross-domain separation paths) of the domain sequence DS(og, j) is (S,BN-ex(og, 1, j), BN-en(og, i, j), BN-ex(og, i, j), BN-en(og, n, j), D);and the shortest path algorithm includes, but is not limited to: theDjkstra algorithm, the Floyd algorithm, the Bellman-Ford algorithm, theShortest Path Faster Algorithm (SPFA) algorithm.

In step 122, the PCE_P uses the path of the DS(og, j) as a separationconstraint condition and computes the pass-through domain sequenceDS(dj, j) of the protection path (here a domain sequence DS(dj, 1) is adomain sequence of the protection path in the first pair of candidatecross-domain separation paths) using the preset shortest path algorithm,and the process continues to perform step 123.

Herein a specific path of the domain sequence DS(dj, 1) is (S, BN-ex(dj,1, j), BN-en(dj, j), BN-ex(dj, i, j), . . . , BN-en(dj, n, j), D); andthe shortest path algorithm can be known with reference to the abovedescription, and will not be repeated here.

In step 123, 1 is added to j, and it is judged whether j+1 is greaterthan K, and if it is judged that j+1 is not greater than K, the processcontinues to perform step 124; and when it is judged that j+1 is greaterthan K, the process ends.

In step 124, the PCE_P computes a domain sequence DS(og, j) of asub-optimal working path with respect to a pass-through domain sequenceDS(og, j−1) of an j−1^(th) working path using the preset K-optimal pathalgorithm, and the process continues to perform step 122, and so on,until the K pairs of candidate separation domain sequences are computed,i.e., j+1 is greater than K in step 123.

In the above solution, the DS(o, j) and the DS(dj, j) are considered tobe a pair of candidate separation domain sequences.

Herein, traversing the K pairs of candidate separation domain sequences,generating corresponding intra-domain path computation requests forvarious domains in the network, and transmitting an intra-domain pathcomputation request of each domain to a sub-PCE corresponding to thedomain includes:

generating an associated path computation request (association request)each time a pair of candidate separation domain sequences is traversedby the parent PCE such as the PCE_P for an intra-domain path computationrequest of the head domain AS(1); acquiring an association requestgenerated for a j1^(th) pair of candidate sequences, and determining theassociation request as a first association request; acquiring anassociation request generated for a j2^(th) pair of candidate sequences,and determining the association request as a second association request;when in the K pairs of candidate separation domain sequences, an egressboundary node of a working path domain sequence in the j1^(th) pair ofcandidate sequences in the head domain is the same as an egress boundarynode of a working path domain sequence in the j2^(th) pair of candidatesequences in the head domain, and an egress boundary node of aprotection path domain sequence in the j1^(th) pair of candidatesequences in the head domain is the same as an egress boundary node of aprotection path domain sequence in the j2^(th) pair of candidatesequences in the head domain, merging the first association request andthe second association request into an association request, and mergingall the generated association requests into an intra-domain pathcomputation request, such as SUB_REQ(1), and transmitting theintra-domain path computation request to a sub-PCE which is used tocompute intra-domain paths of the head domain AS(1), such as PCE_S(1),herein j1 and j2 are positive integers, 1≤j1≤K, 1≤j2≤K and j1≠j2.

It can be seen that in the head domain, the intra-domain pathcomputation request includes at least one association request, andassociated paths corresponding to a j^(th) association request may berepresented by ingress and egress boundary nodes in the j^(th) pair ofcandidate separation domain sequences in the head domain. For example,in the associated paths corresponding to the j^(th) association request,a working path may be expressed as: <S, BN-ex(og, 1, j)> and aprotection path may be expressed as <S, BN-ex(dj, 1, j)>. In j1^(th) andj2^(th) associated paths, if for working paths, BN-ex(og, 1,j1)=BN-ex(og, 1, j2), and for protection paths, BN-ex(dj, 1,j1)=BN-ex(dj, 1, j2), the j1^(th) association request and the j2^(th)association request are merged into an association request.

Generating an associated path computation request (association request)each time a pair of candidate separation domain sequences is traversedby the parent PCE such as the PCE_P for an intra-domain path computationrequest of the tail domain AS(n); acquiring an association requestgenerated for a j1^(th) pair of candidate sequences, and determining theassociation request as a first association request; acquiring anassociation request generated for a j2^(th) pair of candidate sequences,and determining the association request as a second association request;when in the K pairs of candidate separation domain sequences, an ingressboundary node of a working path domain sequence in the j1^(th) pair ofcandidate sequences in the tail domain is the same as an ingressboundary node of a working path domain sequence in the j2^(th) pair ofcandidate sequences in the tail domain, and an ingress boundary node ofa protection path domain sequence in the j1^(th) pair of candidatesequences in the tail domain is the same as an ingress boundary node ofa protection path domain sequence in the j2^(th) pair of candidatesequences in the tail domain, merging the first association request andthe second association request into an association request, and mergingall the generated association requests into an intra-domain pathcomputation request, such as SUB_REQ(n), and transmitting theintra-domain path computation request to a sub-PCE which is used tocompute intra-domain paths of the tail domain AS(n), such as PCE_S(n).

It can be seen that in the tail domain, the intra-domain pathcomputation request includes at least one association request, andassociated paths corresponding to a j^(th) association request may berepresented by ingress and egress boundary nodes of the j^(th) pair ofcandidate separation domain sequences in the tail domain. For example,in the associated paths corresponding to the j^(th) association request,a working path may be expressed as: <BN-en(og, n, j), D> and aprotection path may be expressed as <BN-en(dj, n, j), D>. In j1^(th) andj2^(th) associated paths, if for working paths, BN-en(og, n,j1)=BN-en(og, n, j2), and for protection paths, BN-en(dj, n,j1)=BN-en(dj, n, j2), the j1^(th) association request and the j2^(th)association request are merged into an association request.

For an intra-domain path computation request of an intermediate domainAS(ii), herein 1<ii<n, the parent PCE, such as the PCE_P, generates anassociated path computation request (association request) and/or annon-associated path computation request (non-association request) eachtime a pair of candidate separation domain sequences is traversed, andall the generated association requests and/or non-association requestsare merged into an intra-domain path computation request such as theSUB_REQ(ii).

Specifically, when the working path domain sequence DS(og, j) and theprotection path domain sequence DS(dj, j) in the j^(th) pair ofcandidate separation domain sequences pass through the domain AS(ii),the parent PCE generates an association request for the j^(th) pair ofcandidate separation domain sequences DS(og, j) and DS(dj, j); acquiresan association request generated for the j1^(th) pair of candidatesequences, and determines the association request as a first associationrequest; acquires an association request generated for the j2^(th) pairof candidate sequences, and determines the association request as asecond association request; when in at least two pairs of candidateseparation domain sequences in which working path domain sequences andprotection path domain sequences all pass through the intermediatedomain, ingress and egress boundary nodes of the working path domainsequence in the j1^(th) pair of candidate sequences in the domain AS(ii)are the same as ingress and egress boundary nodes of the working pathdomain sequence in the j2^(th) pair of candidate sequences in the domainAS(ii), and ingress and egress boundary nodes of the protection pathdomain sequence in the j1^(th) pair of candidate sequences in the domainAS(ii) are the same as ingress and egress boundary nodes of theprotection path domain sequence in the j2^(th) pair of candidatesequences in the domain AS(ii), the first association request and thesecond association request are merged into an association request, allthe generated association requests are merged into an intra-domain pathcomputation request such as the SUB_REQ(ii), and the intra-domain pathcomputation request is transmitted to a sub-PCE which is used to computeintra-domain paths of the domain AS(ii) such as the PCE_S(ii).

It can be seen that when the working path domain sequence DS(og, j) andthe protection path domain sequence DS(dj, j) in the j^(th) pair ofcandidate separation domain sequences pass through the domain AS(ii),associated paths corresponding to the j^(th) association request may berepresented by ingress and egress boundary nodes of the j^(th) pair ofcandidate separation domain sequences in the domain AS(ii). For example,in the associated paths corresponding to the j^(th) association request,the working path may be expressed as <BN-en(og, ii, j), BN-ex(og, ii,j)> and the protection path may be expressed as <BN-en(dj, ii, j),BN-ex(dj, ii, j)>. In the j1^(th) and j2^(th) associated paths, if forthe working paths, BN-en(og, ii, j1)=BN-en(og, ii, j2) and BN-ex(og, iij1)=BN-ex(og, ii, j2), and for the protection paths, BN-en(dj, ii,j1)=BN-en(dj, ii, j2) and BN-ex(dj, ii, j1)=BN-ex(dj, ii, j2), thej1^(th) association request and the j2^(th) association request aremerged into an association request.

When only one of the working path domain sequence DS(og, j) and theprotection path domain sequence DS(dj, j) in the j^(th) pair ofcandidate separation domain sequences passes through the intermediatedomain AS(ii), a single path computation request (non-associationrequest) in the domain AS(ii) is generated for a domain sequence whichpasses through the intermediate domain AS(ii), herein thenon-association request may be an independent path computation request(independent request), and the request is merged into SUB_REQ(ii).Herein, a non-association request generated for a working path domainsequence/protection path domain sequence of a j1^(th) pair of candidatesequences is acquired, and is determined as a first non-associationrequest; a non-association request generated for a working path domainsequence/protection path domain sequence of a j2^(th) pair of candidatesequences is acquired, and is determined as a second non-associationrequest; and when ingress and egress boundary nodes of the workingpath/protection path domain sequence in the j1^(th) pair of candidatesequences are the same as ingress and egress boundary nodes of theworking path/protection path domain sequence in the j2^(th) pair ofcandidate sequences, the first non-association request and the secondnon-association request are merged, and the merged non-associationrequest is transmitted to a sub-PCE which is used for computation ofintra-domain paths of the domain AS(ii), such as the PCE_S(ii).

It can be seen that when only one of the working path domain sequenceDS(og, j) and the protection path domain sequence DS(dj, j) of thej^(th) pair of candidate separation domain sequences passes through theintermediate domain AS(ii), a non-association path corresponding to thej^(th) non-association request may be represented by ingress and egressboundary nodes of the j^(th) pair of candidate separation domainsequences in the domain AS(ii). For example, when only DS(og, j) passesthrough the intermediate domain AS(ii), the non-association pathcorresponding to the j^(th) non-association request may be representedby <BN-en(og, ii, j), BN-ex(og, ii, j)>. For example, when DS(dj, j)passes through the domain AS(ii), the non-association path correspondingto the j^(th) non-association request may be represented by <BN-en(dj,ii, j), BN-ex(dj, ii, j)>. When only DS(dj, j1) of the j1^(th) pair ofcandidate separation domain sequences and only DS(dj, j2) of the j2^(th)pair of candidate separation domain sequences pass through the domainAS(ii) and BN-en(dj, ii, j1)=BN-en(dj, ii, j2) and BN-ex(dj, ii,j1)=BN-ex(dj, ii, j2), the non-association request generated for DS(dj,j1) and the non-association request generated for DS(dj, j2) in thedomain AS(ii) are merged.

In step 13, each of the at least one sub-PCE determines a type of theintra-domain path computation request received by itself, acquires atleast one pair of intra-domain paths in a domain administered by itselfaccording to the type and domain boundary nodes carried in theintra-domain path computation request, and transmits the acquiredintra-domain paths to the parent PCE.

In an embodiment, when the PCE_S(i) responsible for computing eachsub-domain AS(i) receives an intra-domain path computation requestSUB_REQ(i) from the PCE_P, herein 1≤i≤n, for the associated pathcomputation request, disjoint working path and protection pathcorresponding to the working path (intra-domain paths) in the domainAS(i) are computed according to boundary nodes which ingress and egressthe domain AS(i) carried in the association request using thesimultaneous disjoint path algorithm; and for the non-associated pathcomputation request, a single intra-domain path within the domain AS(i)is computed using the shortest path algorithm and/or K-optimal pathalgorithm; and each PCE_S(i) returns a computation result of itself tothe parent PCE, such as the PCE_P, in a response form of SUB_RSP(ii)through a standard protocol PCEP message.

Herein, for a sub-PCE, such as PCE_S(1), which is responsible forcomputing the head domain AS(1), a type of an intra-domain pathcomputation request received by the PCE_S(1) itself is an associationrequest, and for the association request, disjoint working path andprotection path corresponding to the working path (intra-domain paths)in the head domain are computed for each association request accordingto an egress boundary node of the head domain carried in the associationrequest using the simultaneous disjoint path algorithm. Specifically, inthe head domain AS(1), for the j^(th) associated path computationrequest (<S, BN-ex(og, 1, j)>, <S, BN-ex(dj, 1, j)>), as shown in FIG.3(a), a virtual node VNXj is newly added in an intra-domain topology ofthe head domain AS(1) as a tail node of the domain AS(1). As a result,two newly added virtual links appear, herein a first newly added virtuallink connects BN-ex(og, 1, j) and VNXj, and a second newly added virtuallink connects BN-ex(dj, 1, j) and VNXj. A link cost value is preset to acertain positive integer which is much less than a minimum intra-domainlink cost value. An intra-domain path computation topology of the headdomain is formed according to the virtual node and the two newly addedvirtual links. The intra-domain path computation topology of the headdomain includes the virtual node VNXj, the two newly added virtual linksand the intra-domain topology of the head domain.

In the intra-domain path computation topology of the head domain AS(1),a pair of shortest disjoint paths Pin′(og, 1, j) and Pin′(dj, 1, j) fromthe head node S to the virtual node VNXj is computed using thesimultaneous disjoint path algorithm, and a path Pin(og, 1, j) from thehead node S to an egress boundary node BN-ex(og, 1, j) of the headdomain AS(1) (a first egress boundary node of the head domain) isseparated therefrom, herein Pin(og, 1, j) is an intra-domain workingpath of the head domain AS(1), and PKey(og, 1, j) is generated as afirst PathKey; a path Pin(dj, 1, j) from the head node S to an egressboundary node BN-ex(dj, 1, j) of the head domain AS(1) (a second egressboundary node of the head domain) is separated from Pin′(dj, 1, j),herein Pin(dj, 1, j) is an intra-domain protection path of the headdomain AS(1), and PKey(dj, 1, j) is generated as a second PathKey; andthe first PathKey and the second PathKey are returned to the PCE_P asthe j^(th) pair of intra-domain paths corresponding to the j^(th) pairof candidate separation domain sequences; herein the intra-domainworking path Pin(og, 1, j) and intra-domain protection path Pin(dj, 1,j) are used as intra-domain paths in the head domain AS(1).

Herein, for a sub-PCE, such as PCE_S(n), which is responsible forcomputing the tail domain AS(n), a type of an intra-domain pathcomputation request received by the PCE_S(n) itself is an associationrequest, and for the association request, disjoint working path andprotection path corresponding to the working path(intra-domain paths) inthe tail domain are computed for each association request according toan ingress boundary node of the tail domain carried in the associationrequest using the simultaneous disjoint path algorithm. Specifically, inthe tail domain AS(n), for the j^(th) associated path computationrequest(<BN-en(og, n, j), D>, <S, BN-en(dj, n, j), D>), as shown in FIG.3(b), a virtual node VNEj is newly added in an intra-domain topology ofthe tail domain AS(n) as a head node of the domain AS(n). As a result,two newly added virtual links appear, herein a first newly added virtuallink connects the virtual node VENj and BN-en(og, n, j), and a secondnewly added virtual link connects the virtual node VENj and BN-en(dj, n,j). A link cost is preset to a certain positive integer which is muchless than a minimum intra-domain link cost value. An intra-domain pathcomputation topology of the tail domain is formed according to thevirtual node VNEj and the two newly added virtual links. Theintra-domain path computation topology of the tail domain includes thetwo newly added virtual links, the virtual node, and the intra-domaintopology of the tail domain.

In the intra-domain path computation topology of the tail domain, a pairof shortest disjoint paths Pin′(og, n, j) and Pin′(dj, n, j) from thevirtual node VNEj to the tail node D is computed using the simultaneousdisjoint path algorithm, and a path Pin(og, n, j) from an ingressboundary node BN-en(og, n, j) of the tail domain AS(n) (a first ingressboundary node of the tail domain) to the tail node D is separatedtherefrom, herein Pin(og, n, j) is an intra-domain working path in thetail domain AS(n), and PKey(og, n, j) is generated as a first PathKey; apath Pin(dj, n, j) from the an ingress boundary node BN-en(dj, n, j) ofthe tail domain AS(n) (a second ingress boundary node of the taildomain) to the tail node D is separated from Pin′(dj, n, j), herein pathPin(dj, n, j) is an intra-domain protection path in the tail domainAS(n), and PKey(dj, n, j) is generated as a second PathKey; and thefirst PathKey and the second PathKey are returned to the PCE_P as thej^(th) pair of intra-domain paths corresponding to the j^(th) pair ofcandidate separation domain sequences; herein the intra-domain workingpath Pin(og, n, j) and intra-domain protection path Pin(dj, n, j) areused as intra-domain paths in the tail domain AS(n).

Herein, for a sub-PCE such as PCE_S(ii), which is responsible forcomputing the intermediate domain AS(ii), where 1<ii<n, a type of theintra-domain path computation request received by the PCE_S(ii) itselfmay be an association request type or a non-association request type;for the association request, disjoint working path and protection pathcorresponding to the working path (intra-domain paths) in the domainAS(ii) are computed for each association request according to boundarynodes which ingress and egress the domain AS(ii) carried in theassociation request using the simultaneous disjoint path algorithm; andfor the non-associated paths, a single intra-domain path in the AS(ii)is computed according to the boundary nodes which ingress and egress thedomain carried in the non-association request using the shortest pathalgorithm and/or the K-optimal path algorithm.

Specifically, the PCE_S(ii) traverses all the intra-domain pathcomputation requests for the AS(ii) domain, and for the associated pathcomputation request (<BN-en(og, ii, j), BN-ex(og, j)>, <BN-en(dj, ii,j), BN-ex(dj, ii, j)>), as shown in FIG. 3(c), two virtual nodes arenewly added to the intra-domain topology of AS(i), which are a firstvirtual node VNEj and a second virtual node VNXj respectively. Herein,the first virtual node VNEj acts as a head node in the AS(ii) domain andthe second virtual node VNXj acts as a tail node in the AS(ii) domain.As a result, four newly added virtual links appear, herein a first newlyadded virtual link connects VNEj and BN-en(og, ii, j), a second newlyadded virtual link connects VNEj and BN-en(dj, j), a third newly addedvirtual link connects BN-ex(og, ii, j) and VNXj, and a fourth newlyadded virtual link connects BN-ex(dj, ii, j) and VNXj. A link cost ispreset to be a certain positive integer value which is much less than aminimum intra-domain link cost value. An intra-domain path computationtopology of the intermediate domain is formed according to the firstvirtual node VNEj, the second virtual node VNXj, and the four newlyadded virtual links. The intra-domain path computation topology of theintermediate domain includes the four newly added virtual links, thefirst virtual node VNEj, the second virtual node VNXj and theintra-domain topology of the intermediate domain.

In the intra-domain path computation topology of the intermediate domainAS(ii), a pair of shortest disjoint paths Pin′(og, ii, j) and Pin′(dj,ii, j) from the first virtual node VNEj to the second virtual node VNXjis computed using the simultaneous disjoint path algorithm, and a pathPin(og, ii, j) from an ingress boundary node BN-en(og, ii, j) (a firstingress boundary node of the intermediate domain) to an egress boundarynode BN-ex(og, ii, j) (a first egress boundary node of the intermediatedomain) of the working path domain sequence in the j^(th) pair ofcandidate separation domain sequences in the domain AS(ii) is separatedfrom the pair of shortest disjoint paths as the intra-domain workingpath, and a first PathKey is generated, i.e., PKey(og, ii, j); a pathfrom an ingress boundary node BN-en(dj, ii, j) (a second ingressboundary node of the intermediate domain) to an egress boundary nodeBN-ex(dj, ii, j) (a second egress boundary node of the intermediatedomain) of the protection path domain sequence in the j^(th) pair ofcandidate separation domain sequences in the domain AS(ii) is separatedfrom the pair of shortest disjoint paths, herein BN-ex(dj, ii, j) is theintra-domain protection path, and a second PathKey is generated, i.e.,PKey(og, ii, j); and the first PathKey and the second PathKey arereturned to the PCE_P as the j^(th) pair of intra-domain pathscorresponding to the j^(th) pair of candidate separation domainsequences; herein the intra-domain working path Pin(og, ii, j) andintra-domain protection path Pin(dj, ii, j) may be used as intra-domainpaths in the intermediate domain AS(ii).

Here, the PCE_S(ii) traverses all the intra-domain path computationrequests for the AS(ii) domain, and for an non-associated pathcomputation request, the PCE_S(ii) uses paths between boundary nodeswhich ingress and egress the domain in the domain AS(ii) carried in thenon-association request as intra-domain paths in the domain AS(ii), andreturns the intra-domain paths to the PCE_P.

Herein, the simultaneous disjoint path algorithm can be known withreference to the existing related description, and will not be repeatedhere.

In step 14, when at least one pair of intra-domain paths transmitted byeach sub-PCE is received by the parent PCE, the parent PCE configureseach intra-domain path in the at least one pair of intra-domain paths toa corresponding position in the K pairs of candidate separation domainsequences, to form K pairs of candidate cross-domain separation paths;determines a pair of cross-domain separation paths from the K pairs ofcandidate cross-domain separation paths; and transmits the cross-domainseparation paths as a computation result of the cross-domain separationpath computation request to a sub-PCE which is used to administer adomain to which the node belongs.

Here, after the PCE_P collects return results SUB_RSP(i)s from all thePCE_S(i)s, the PCE_P configures intra-domain paths of pass-throughdomains corresponding to the working path domain sequence in the j^(th)pair of candidate separation domain sequences to corresponding positionsof the working path of the j^(th) pair of candidate separation domainsequences, configures intra-domain paths of pass-through domainscorresponding to the protection path domain sequence in the j^(th) pairof candidate separation domain sequences to corresponding positions ofthe protection path of the j^(th) pair of candidate separation domainsequences, and forms a j^(th) pair of candidate cross-domain separationpaths; in the formed K pairs of candidate cross-domain separation paths,a path cost of a working path and a path cost of a protection path ineach pair of candidate cross-domain separation paths are computed; andthe path cost of the working path and the path cost of the protectionpath in each pair of candidate cross-domain separation paths are summedto form a path cost sum; candidate cross-domain separation paths withthe minimum path cost sum are selected as the cross-domain separationpaths; and a cross-domain separation path computation result istransmitted to a corresponding PCE_S(i).

In an embodiment, as in the step 121 described above, a specific path ofthe domain sequence DS(og, j) in the j^(th) pair of candidate separationdomain sequences is (S, BN-ex(og, 1, j), BN-en(og, i, j), BN-ex(og, i,j), . . . , BN-en(og, n, j), D) and a specific path of DS(dj, j)corresponding to the DS(og, j) is (S, BN-ex(dj, 1, j), BN-en(dj, i, j),BN-ex(dj, i, j), . . . , BN-en(dj, n, j), D), the j^(th) pair ofintra-domain paths is configured to corresponding positions in thej^(th) pair of candidate separation domain sequences, to form the j^(th)pair of candidate cross-domain separation paths, for example, theworking path DP(og, j) in the j^(th) pair of candidate cross-domainseparation paths is (S, PKey(og, 1, j), BN-ex(og, 1, j), . . . ,BN-en(og, i, j), PKey(og, j), BN-ex(og, i, j), . . . , BN-en(og, n, j),PKey(og, n, j), D), and the protection path DP(dj, j) in the j^(th) pairof candidate cross-domain separation paths is (S, PKey(dj, 1, j),BN-ex(dj, 1, j), . . . , BN-en(dj, i, j), PKey(dj, i, j), BN-ex(dj, i,j), . . . , BN-en(dj, n, j), PKey(dj, n, j), D); herein, a cost sum ofthe working path DP(og, j) is PM(og, j), and a cost sum corresponding tothe protection path DP(dj, j) is PM(dj, j), the PCE_P selects a pairwith the minimum cost sum, i.e., min(PM(og, j)+PM(dj, j)), and assumingthat a value of j is jmin at this time, candidate cross-domainseparation paths corresponding to DP(og, jmin) and DP(dj, jmin) areobtained, and are used as a computation result for the cross-domainseparation path computation request, and the computation result isreturned to a sub-PCE, such as PCE_S(1), which is used to forward thecross-domain separation path computation request.

In step 15, a sub-PCE which is used to administer a domain to which thenode belongs receives a cross-domain separation path computation resultfor the cross-domain separation path computation request, and transmitsthe cross-domain separation path computation result to the node.

Here, for example the PCE-S(1) returns the cross-domain separation pathcomputation result to the node, such as the head node S, which initiatescomputation for the cross-domain separation path computation request.

It can be seen that the embodiments of the present disclosure determinea final appropriate cross-domain separation path based on thehierarchical PCE conceptual model through interaction between the parentPCE and various sub-PCEs thereof. As the hierarchical PCE conceptualmodel is used, there is no need to acquire a cross-domain end-to-enddomain sequence between head and tail domains in advance. At the sametime, the parent PCE acquires the candidate separation domain sequences,and generate corresponding intra-domain path computation requests forvarious sub-PCEs according to the candidate separation domain sequences,each sub-PCE acquires at least one pair of intra-domain paths of adomain which is administered by itself according to a type of anintra-domain path computation request of itself, and transmits theacquired intra-domain paths to the parent PCE, and the parent PCEconfigures the received intra-domain paths to corresponding positions ofthe candidate separation domain sequences, and determines the finalcross-domain separation path from the candidate cross-domain separationpaths. The parent PCE integrates the computation results of varioussub-PCEs, which improves the success ratio of the acquisition of thecross-domain separation paths (the working path and the protectionpath), thus ensuring the global optimality of path separation.

FIG. 4 is a flowchart of implementation two of a method for acquiring across-domain separation path according to the present disclosure. Themethod is applied in a parent PCE. As shown in FIG. 4, the methodincludes the following steps.

In step 41, when a cross-domain separation path computation request isreceived, K pairs of candidate separation domain sequences are acquiredaccording to a cross-domain network abstraction topology.

In step 42, the K pairs of candidate separation domain sequences aretraversed, corresponding intra-domain path computation requests aregenerated for domains through which various candidate separation domainsequences in the network pass, and the intra-domain path computationrequests of the various domains are transmitted.

In step 43, when at least one pair of intra-domain paths for theintra-domain path computation requests are received, each intra-domainpath in the at least one pair of intra-domain paths is configured to acorresponding position in the K pairs of candidate separation domainsequences, to form K pairs of candidate cross-domain separation paths;and one pair of cross-domain separation paths is determined from the Kpairs of candidate cross-domain separation paths.

In step 44, the cross-domain separation paths are transmitted as acomputation result of the cross-domain separation path computationrequest.

The embodiments of the present disclosure further provide a firstcomputer storage medium having a first set of computer-executableinstructions stored therein, which is used for the above describedmethod for acquiring a cross-domain separation path applied in a parentPCE.

FIG. 5 is a flowchart of implementation three of a method for acquiringa cross-domain separation path according to the present disclosure. Themethod is applied in at least one sub-PCE. As shown in FIG. 5, themethod includes the following steps.

In step 51, when a cross-domain separation path computation requesttransmitted by a node is received, one of the at least one sub-PCE whichis used to administer a domain to which the node belongs transmits thecross-domain separation path computation request.

In step 52, each of the at least one sub-PCE determines a type of theintra-domain path computation request received by itself, acquires atleast one pair of intra-domain paths in a domain administered by itselfaccording to the type and domain boundary nodes carried in theintra-domain path computation request, and transmits the acquiredintra-domain paths.

In step 53, a cross-domain separation path computation result for thecross-domain separation path computation request is received and thereceived cross-domain separation path computation result is transmittedto the node.

The embodiments of the present disclosure further provide a secondcomputer storage medium having a second set of computer-executableinstructions stored therein, which is used for the above describedmethod for acquiring a cross-domain separation path applied in asub-PCE.

It should be illustrated that the above-described specificimplementations of the method for acquiring a cross-domain separationpath applied in at least one sub-PCE and the method for acquiring across-domain separation path applied in a parent PCE etc. can be knownwith reference to the above description of FIGS. 1 to 3, and will not berepeated here.

The above technical solutions can be understood with reference to thefollowing embodiments (embodiment one, embodiment two and embodimentthree) according to the present disclosure.

FIG. 6 is a diagram of embodiment one of a method for acquiring across-domain separation path according to the present disclosure. Theembodiment one belongs to a condition that each of K pairs of candidateseparation domain sequences does not have an association request in theintermediate domain AS(ii).

As shown in FIG. 6, in a current network, there are 16 boundary nodesand there are totally n=4 domains, which are AS(1), AS(2), AS(3) andAS(4) respectively. A distribution of the 16 boundary nodes in the 4domains is shown in the figure. Each domain has a corresponding sub-PCE,and they are PCE_S(1), PCE_S(2), PCE_S(3), and PCE_S(4), respectively.In the current network, there is a parent PCE, i.e., PCE_P, which isused to manage the four sub-PCEs. Herein, a node S is a head node forthe cross-domain separation path computation, and is located in the headdomain AS(1), and a node D is a destination node (tail node) for thecross-domain separation path computation, and is located in the taildomain AS(4).

In step 601, the head node S sends a cross-domain separation pathcomputation request DPC_REQ(S, D) to the PCE_S(1).

In step 602, the PCE_S(1) transmits the cross-domain separation pathcomputation request to the PCE_P.

In step 603, the PCE_P receives the cross-domain separation pathcomputation request, and firstly computes K pairs of candidateseparation domain sequences using the sequential path computationaccording to an inter-domain topology consisted of ingress and egressboundary nodes and inter-domain links of various domains, herein pathsthrough which the K pairs of candidate separation domain sequences passare K pairs of candidate cross-domain separation paths.

Here, K is preset to be 2, j is initialized to be 1, and the PCE_Pcomputes a pass-through domain sequence DS(o, j=1) of a working path ina j=1^(st) pair of candidate cross-domain separation paths from a headnode S to a tail node D, herein a specific path of the domain sequenceDS(o, j=1) is a boundary node sequence (S, BN1, BN5, BN7, BN13, D)illustrated in FIG. 6; and the PCE_P computes a domain sequence DS(dj,j=1) of a protection path in the j=1^(st) pair of candidate cross-domainseparation paths from a head node S to a tail node D using the paths ofthe DS(og, 1) as a separation constraint condition using the shortestpath algorithm, herein a specific path of the domain sequence DS(dj,j=1) is a boundary node sequence (S, BN3, BN9, BN11, BN15, D)illustrated in FIG. 6.

Then, PCE_P adds 1 to j (j+1=1+1=2), and judges that j+1 is equal to 2;computes a working path DS domain sequence (og, 2) which is sub-optimalrelative to a working path domain sequence DS(og, 1) using the K-optimalpath algorithm, and uses the DS(og, 2) as a domain sequence of a workingpath in a second pair of separation paths, herein a specific path of thedomain sequence DS(og, 2) is a boundary node sequence (S, BN2, BN6, BN8,BN14, D) illustrated in FIG. 6; and the PCE_P computes a domain sequenceDS(dj, 2) of a protection path in a j=2^(nd) pair of separation pathsfrom S to D using the shortest path algorithm by taking paths of DS(og,2) as a separation constraint condition, herein a specific path of thedomain sequence DS(dj, 2) is a boundary node sequence (S, BN4, BN10,BN12, BN16, D) illustrated in FIG. 6, and the PCE_P adds 1 to j(j+1=2+1=3), and judges that j+1 is greater than K=2, and the processends.

At this point, the PCE_P totally computes 2 pairs of candidateseparation domain sequences, each pair of candidate separation domainsequences corresponding to a candidate cross-domain separation path. Asshown in FIG. 6, the black bold solid line in the figure is the workpath in the candidate cross-domain separation paths, the black bolddotted line is the protection path in the candidate cross-domainseparation paths, and the thin dotted line represents the intra-domainpaths.

In step 604, the PCE_P traverses the 2 pairs of candidate separationdomain sequences, generates corresponding intra-domain path computationrequests for the 4 domains in the current network, and transmits theintra-domain path computation requests for the 4 domains tocorresponding sub-PCEs.

Here, for the head domain AS(1), an association computation request(association request) REQ_ID1-1 is generated, which is <S-BN1, S-BN3>for the j=1^(st) pair of candidate separation domain sequences, and anassociation computation request REQ_ID1-2 is generated, which is <S-BN2,S-BN4> for the j=2^(nd) pair of candidate separation domain sequences,and therefore, two association computation requests are included in theintra-domain path computation request SUB_REQ(1) transmitted to thesub-PCE, i.e., PCE_S(1).

For the tail domain AS(4), an association computation request REQ_ID4-1is generated, which is <BN13-D, BN15-D> for the j=1^(st) pair ofcandidate separation domain sequences, and an association computationrequest REQ_ID4-2 is generated, which is <BN14-D, BN16-D> for thej=2^(nd) pair of candidate separation domain sequences, and therefore,two association computation requests are included in the intra-domainpath computation request SUB_REQ(4) transmitted to the sub-PCE, i.e.,PCE_S(4).

For an intermediate domain AS(ii=2), a non-association computationrequest (non-association request), i.e., an independent requestREQ_ID2-1 is generated, which is <BN5-BN7> for the j=1^(st) pair ofcandidate separation domain sequences, and an independent requestREQ_ID2-2 is generated, which is <BN6-BN8> for the j=2^(nd) pair ofcandidate separation domain sequences, and therefore, two independentrequests are included in the intra-domain path computation requestSUB_REQ(2) transmitted to the sub-PCE, i.e., PCE_S(2).

For an intermediate domain AS(ii=3), a non-association computationrequest (non-association request), i.e., an independent request RREQ_ID3-1 is generated, which is <BN9-BN11> for the j=1^(st) pair ofcandidate separation domain sequences, and an independent requestREQ_ID3-2 is generated, which is <BN10-BN12> for the j=2^(nd) pair ofcandidate separation domain sequences, and therefore, two independentrequests are included in the intra-domain path computation requestSUB_REQ(3) transmitted to the sub-PCE, i.e., PCE_S(3).

In step 605, each sub-PCE determines a type of the intra-domain pathcomputation request received by itself, acquires at least one pair ofintra-domain paths of a domain administered by itself according to thetype and domain boundary nodes carried in the intra-domain pathcomputation request, and transmits the acquired at least one pair ofintra-domain paths to the parent PCE.

Here, two association requests REQ_ID1-1 and REQ_ID1-2 are included inthe intra-domain path computation request SUB_REQ(1) received by thesub-PCE responsible for intra-domain path computation of the head domainAS(1), i.e., the PCE_S(1). For a condition that REQ_ID1-1 is <S-BN1,S-BN3>, with reference to the description of FIG. 3(a), in theintra-domain topology in the head domain AS(1), a virtual node VNXj isnewly added as a tail node in the AS(1) domain. As a result, two newlyadded virtual links appear, herein the first newly added virtual linkconnects BN1 and VNXj(j=1), and the second newly added virtual linkconnects BN3 and VNXj(j=1). In the intra-domain path computationtopology of the head domain in which the two newly added virtual links,the virtual node VNXj and the intra-domain topology of the head domainare included, a pair of shortest disjoint paths Pin′(og, 1, j=1) andPin′(dj, 1, j=1) from the head node S to the virtual node VNXj(j=1) iscomputed using the simultaneous disjoint path algorithm, a path Pin(og,1, 1) (which is an intra-domain working path) from the head node S to anegress boundary node BN1 of the head domain AS(1) is separatedtherefrom, and PKey(og, 1, 1) is generated as a first PathKey; and apath Pin(dj, 1, 1) (which is an intra-domain protection path) from thehead node S to an egress boundary node BN3 of the head domain AS(1) isseparated from Pin′(dj, 1, 1), a second PKey(dj, 1, 1) is generated as aPathKey, and the first PKey(og, 1, 1) and the second PKey(dj, 1, 1) areencapsulated into DPC_RSP(1) as a j=1^(st) pair of intra-domain pathscorresponding to the j=1^(st) pair of candidate separation domainsequences in the head domain AS(1). For a condition that REQ_ID1-2 is<S-BN2, S-BN4>, similarly, the first PKey(og, 1, 2) and the secondPKey(1, 2) are separated from the pair of shortest disjoint paths usingthe above method of adding a virtual node, to acquire PKey(og, 1, 2) andPKey(dj, 1, 2) of a j=2^(nd) pair of intra-domain paths corresponding toa j=2^(nd) pair of candidate separation domain sequences in the headdomain AS(1), PKey(og, 1, 2) and PKey(dj, 1, 2) are encapsulated intoDPC_RSP(1), and the DPC_RSP(1) is returned to the PCE_P.

Two association requests REQ_ID4-1 and REQ_ID4-2 are included in theintra-domain path computation request SUB_REQ(4) received by the sub-PCEresponsible for intra-domain path computation of the tail domain AS(4),i.e., the PCE_S(4). For a condition that REQ_ID4-1 is <BN13-D, BN15-D>,with reference to the description of FIG. 3(b), in the intra-domaintopology in the tail domain AS(4), a virtual node VNEj is newly added asa head node in the AS(4) domain. As a result, two newly added virtuallinks appear, herein the first newly added virtual link connects VNEjand BN13, and the second newly added virtual link connects VNEj andBN15. In the intra-domain path computation topology of the tail domainin which the two newly added virtual links, the virtual node VNEj andthe intra-domain topology of the tail domain are included, a pair ofshortest disjoint paths Pin′(og, 4, j=1) and Pin′(dj, 4, j=1) from thevirtual node VNEj to the tail node D is computed using the simultaneousdisjoint path algorithm, a path Pin(og, 4, 1) (which is an intra-domainworking path) from the node BN13 to the tail node D is separated fromPin′(og, 4, j=1), and PKey(og, 4, 1) is generated as a first PathKey;and a path Pin(dj, 4, 1) from the node BN15 to the tail node D isseparated from Pin′(dj, 4, 1), PKey(dj, 4, 1) is generated as a secondPathKey, and the PKey(og, 4, 1) and the PKey(dj, 4, 1) are encapsulatedinto DPC_RSP(4) as a j=1^(st) pair of intra-domain paths correspondingto the j=1^(st) pair of candidate separation domain sequences in thetail domain AS(4). For a condition that REQ_ID4-2 is <BN14-D, BN16-D>,similarly, the intra-domain working path Pin(og, 4, 2) and theintra-domain protection path Pin(dj, 4, 2) are separated from the pairof shortest disjoint paths using the above method of adding a virtualnode, PKey(og, 4, 2) is generated as the first PathKey and PKey(dj, 4,2) is generated as the second PathKey, and PKey(og, 4, 2) and PKey(dj,4, 2) of a j=2^(nd) pair of intra-domain paths corresponding to aj=2^(nd) pair of candidate separation domain sequences acquired in thetail domain AS(4) are encapsulated into DPC_RSP(4), and the DPC_RSP(4)is returned to the PCE_P.

The intra-domain path computation requests received by the sub-PCEresponsible for the intra-domain path computation of the intermediatedomain AS(2), i.e., the PCE_S(2), are two independent requests,including REQ_ID2-1 which is <BN5-BN7> and REQ_ID2-2 which is <BN6-BN8>.Herein, for the <BN5-BN7>, the intra-domain paths of the boundary nodesBN5 to BN7 are computed using the shortest path algorithm to acquire theintra-domain paths of the boundary nodes BN5 to BN7 as Pin(og, 2, 1),and PKey(og, 2, 1) is generated as the corresponding PathKey and isencapsulated in SUB_RSP(2). For the <BN6-BN8>, the intra-domain paths ofboundary nodes BN6 to BN8 are acquired using the same method as Pin(og,2, 2), PKey(og, 2, 2) is generated as the corresponding PathKey and isencapsulated into SUB_RSP(2), and the SUB_RSP(2) is returned to thePCE_P.

The intra-domain path computation requests received by the sub-PCEresponsible for the intra-domain path computation of the intermediatedomain AS(3), i.e., the PCE_S(3), are two independent requests,including REQ_ID2-1 which is <BN9-BN11> and REQ_ID2-2 which is<BN10-BN12>. Herein, for the <BN9-BN11>, the intra-domain paths of theboundary nodes BN9 to BN11 are computed using the shortest pathalgorithm to acquire the intra-domain paths of the boundary nodes BN9 toBN11 as Pin(og, 3, 1), and PKey(og, 3, 1) is generated as thecorresponding PathKey and is encapsulated in SUB_RSP(3). For the<BN10-BN12>, the intra-domain paths of boundary nodes BN10 to BN12 areacquired using the same method as Pin(og, 3, 2), PKey(og, 3, 2) isgenerated as the corresponding PathKey and is encapsulated intoSUB_RSP(3), and the SUB_RSP(3) is returned to the PCE_P.

In step 606, the PCE_P receives the SUB_RSPs(1)-(4) transmitted by thesub-PCEs(1)-(4), and configures each intra-domain path of the at leastone pair of intra-domain paths to corresponding positions in the K=2pairs of candidate separation domain sequences to form K pairs ofcandidate cross-domain separation paths; determines a pair ofcross-domain separation paths from the K=2 pairs of candidatecross-domain separation paths; and transmits the cross-domain separationpaths to the sub-PCE which is used for the head node S, i.e., thePCE_S(1), as a computation result for the cross-domain separation pathcomputation request, and the PCE_S(1) then transmits the computationresult to the head node S.

Here, the intra-domain PathKey is configured to the correspondingposition in a K^(th) pair of candidate separation domain sequences toform K=2 pairs of candidate cross-domain separation paths; herein aworking path DP(og, 1) in the first pair of candidate cross-domainseparation paths is (S, PKey(og, 1, 1), BN1, BN5, PKey(og, 2, 1), BN7,BN13, PKey(og, 4, 1), D); a protection path DP(dj, 1) in the first pairof candidate cross-domain separation paths is (S, PKey(dj, 1, 1), BN3,BN9, PKey(dj, 3, 1), BN11, BN15, PKey(dj, 4, 1), D); a working pathDP(og, 2) in the second pair of candidate cross-domain separation pathsis (S, PKey(og, 1, 2), BN2, BN6, PKey(og, 2, 2), BN8, BN14, PKey(og, 4,2), D); and a protection path DP(dj, 2) in the second pair of candidatecross-domain separation paths is (S, PKey(dj, 1, 2), BN4, BN10, PKey(dj,3, 2), BN12, BN16, PKey(dj, 4, 2), D).

The PCE_P sums path costs of the two pairs of candidate cross-domainseparation paths respectively, and takes a pair with the minimum costsum. If PM(og, j)+PM(dj, j)(j=2) is a minimum cost sum, i.e., the PCE_Pdetermines that the second pair of candidate cross-domain separationpaths DP(og, 2) and DP(dj, 2) from the two pairs of candidatecross-domain separation paths as a final cross-domain separation pathcomputation result, encapsulates the computation result in DPC_RSP(S,D), and transmits the DPC_RSP(S, D) to the PCE_S(1). The PCE_S(1)returns the DPC_RSP(S, D) in which the final cross-domain separationpath computation result is encapsulated to the head node S whichinitiates the cross-domain separation path computation request.

It can be seen that the embodiments of the present disclosure determinea final appropriate cross-domain separation path based on thehierarchical PCE conceptual model through interaction between the parentPCE and various sub-PCEs thereof, which improves the success ratio ofthe acquisition of the cross-domain separation paths, thus ensuring theglobal optimality of path separation. Due to the use of the hierarchicalPCE conceptual model, a cross-domain end-to-end domain sequence betweena head domain and a tail domain needs not to be known in advance.

FIG. 7 is a diagram of embodiment two of a method for acquiring across-domain separation path according to the present disclosure. Theembodiment two belongs to a condition that an intra-domain pathcomputation request of each of K pairs of candidate separation domainsequences in the intermediate domain AS(ii) is an associationcomputation request.

As shown in FIG. 7, in a current network, there are 8 boundary nodes andthere are totally n=3 domains, which are AS(1), AS(2) and AS(3)respectively. A distribution of the 8 boundary nodes in the 3 domains isshown in the figure. Various domains correspond to respective sub-PCEs,which are PCE_S(1), PCE_S(2), and PCE_S(3), respectively. In the currentnetwork, there is a parent PCE, i.e., PCE_P, which is used to manage thethree sub-PCEs. Herein, a node S is a head node for the cross-domainpath computation, and is located in the head domain AS(1), and a node Dis a destination node (tail node) for the cross-domain path computation,and is located in the tail domain AS(3).

In step 701, the head node S sends a cross-domain separation pathcomputation request DPC_REQ(S, D) to the PCE_S(1).

In step 702, the PCE_S(1) transmits the cross-domain separation pathcomputation request to the PCE_P.

In step 703, the PCE_P receives the cross-domain separation pathcomputation request, and firstly computes K pairs of candidateseparation domain sequences using the sequential path computationaccording to an inter-domain topology consisted of ingress and egressboundary nodes and inter-domain links of various domains, herein pathsthrough which the K pairs of candidate separation domain sequences passare K pairs of candidate cross-domain separation paths.

Here, K is preset to be 2, j is initialized to be 1, and the PCE_Pcomputes a pass-through domain sequence DS(o, j=1) of a working path ina j=1^(st) pair of candidate cross-domain separation paths from a headnode S to a tail node D, herein a specific path of the domain sequenceDS(o, j=1) is a boundary node sequence (S, BN1, BN3, BN5, BN7, D)illustrated in FIG. 7; and the PCE_P computes a domain sequence DS(dj,j=1) of a protection path in the j=1^(st) pair of candidate cross-domainseparation paths from a head node S to a tail node D using the paths ofthe DS(og, 1) as a separation constraint condition using the shortestpath algorithm, herein a specific path of the domain sequence DS(dj,j=1) is a boundary node sequence (S, BN2, BN4, BN6, BN8, D) illustratedin FIG. 7.

Then, PCE_P adds 1 to j (j+1=1+1=2), and judges that j+1 is equal to 2;computes a working path DS domain sequence (og, 2) which is sub-optimalrelative to a working path domain sequence DS(og, 1) using the K-optimalpath algorithm, and uses the DS(og, 2) as a domain sequence of a workingpath in a second pair of separation paths, herein a specific path of thedomain sequence DS(og, 2) is a boundary node sequence (S, BN2, BN4, BN6,BN8, D) illustrated in FIG. 7; and the PCE_P computes a domain sequenceDS(dj, 2) of a protection path in a j=2^(nd) pair of separation pathsfrom S to D using the shortest path algorithm by taking paths of DS(og,2) as a separation constraint condition, herein a specific path of thedomain sequence DS(dj, 2) is a boundary node sequence (S, BN1, BN3, BN5,BN7, D) illustrated in FIG. 7, and the PCE_P adds 1 to j (j+1=2+1=3),and judges that j+1 is greater than K=2, and the process ends.

At this point, the PCE_P totally computes 2 pairs of candidateseparation domain sequences, each pair of candidate separation domainsequences corresponding to a candidate cross-domain separation path. Asshown in FIG. 7, the black bold solid line in the figure is the workpath in the candidate domain separation paths, the black bold dottedline is the protection path in the candidate cross-domain separationpaths, and the thin dotted line represents the intra-domain paths.

In step 704, the PCE_P traverses the 2 pairs of candidate separationdomain sequences, generates corresponding intra-domain path computationrequests for the 3 domains in the current network, and transmits theintra-domain path computation requests for the 3 domains tocorresponding sub-PCEs.

In the present embodiment, the particularity of the network topologyenables the working path domain sequence DS(og, 1) in the first pair ofcandidate separation domain sequences to coincide with the protectionpath domain sequence DS(dj, 2) in the second pair of candidateseparation domain sequences, and the working path domain sequence DS(og,2) in the second pair of candidate separation domain sequences tocoincide with the protection path domain sequence DS(dj, 1) in the firstpair of candidate separation domain sequences.

In the head domain AS(1), an association computation request(association request) REQ_ID1-1 generated for the j=1^(st) pair ofcandidate separation domain sequences and an association requestREQ_ID1-2 generated for the j=2^(nd) pair of candidate separation domainsequences are merged, and only one association request REQ_ID1-1 isincluded in the intra-domain path computation request SUB_REQ(1)transmitted to the sub-PCE, i.e., PCE_S(1), which is <S-BN1, S-BN2>.

In the tail domain AS(3), an association computation request(association request) REQ_ID3-1 generated for the j=1^(st) pair ofcandidate separation domain sequences and an association requestREQ_ID3-2 generated for the j=2^(nd) pair of candidate separation domainsequences are merged, and only one association request REQ_ID3-1 isincluded in the intra-domain path computation request SUB_REQ(3)transmitted to the sub-PCE, i.e., PCE_S(3), which is <BN7-D, BN8-D>.

In an intermediate domain AS(2), an association computation request(association request) REQ_ID2-1 generated for the j=1^(st) pair ofcandidate separation domain sequences and an association requestREQ_ID2-2 generated for the j=2^(nd) pair of candidate separation domainsequences are merged, and only one association request REQ_ID2-1 isincluded in the intra-domain path computation request SUB_REQ(2)transmitted to the sub-PCE, i.e., PCE_S(2), which is <BN3-BN5, BN4-BN6>.

In step 705, each sub-PCE determines a type of the intra-domain pathcomputation request received by itself, acquires at least one pair ofintra-domain paths of a domain administered by itself according to thetype and domain boundary nodes carried in the intra-domain pathcomputation request, and transmits the acquired at least one pair ofintra-domain paths to the parent PCE.

Here, an association request REQ_ID1-1 is included in the intra-domainpath computation request SUB_REQ(1) received by the sub-PCE responsiblefor intra-domain path computation of the head domain AS(1), i.e., thePCE_S(1). For the association computation request <S-BN1, S-BN2>, withreference to the description of FIG. 3(a), in the intra-domain topologyin the head domain AS(1), a virtual node VNXj is newly added as a tailnode in the AS(1) domain. As a result, two newly added virtual linksappear, herein the first newly added virtual link connects BN1 and VNXj,and the second newly added virtual link connects BN2 and VNXj. In theintra-domain path computation topology of the head domain in which thetwo newly added virtual links, the virtual node VNXj and theintra-domain topology of the head domain are included, a pair ofshortest disjoint paths Pin′(og, 1, j=1) and Pin′(dj, 1, j=1) from thehead node S to the virtual node VNXj(j=1) is computed using thesimultaneous disjoint path algorithm, a path Pin(og, 1, 1) (which is anintra-domain working path) from the head node S to an egress boundarynode BN1 of the head domain AS(1) is separated therefrom, and PKey(og,1, 1) is generated as a first PathKey; and a path Pin(dj, 1, 1) (whichis an intra-domain protection path) from the head node S to an egressboundary node BN2 of the head domain AS(1) is separated from Pin′(dj, 1,1), PKey(dj, 1, 1) is generated as a second PathKey, and the firstPathKey and the second PathKey are encapsulated into DPC_RSP(1) as aj=1^(st) pair of intra-domain paths corresponding to the j=1^(st) pairof candidate separation domain sequences in the head domain AS(1). TheDPC_RSP(1) is returned to the PCE_P.

Here, an association request REQ_ID3-1 is included in the intra-domainpath computation request SUB_REQ(3) received by the sub-PCE responsiblefor intra-domain path computation of the tail domain AS(3), i.e., thePCE_S(3). For the association request <BN7-D, BN8-D>, with reference tothe description of FIG. 3(b), in the intra-domain topology in the taildomain AS(3), a virtual node VNEj is newly added as a head node in theAS(3) domain. As a result, two newly added virtual links appear, hereinthe first newly added virtual link connects the virtual node VNEj(j=1)and BN7, and the second newly added virtual link connects VNEj(j=1) andBN8. In the intra-domain path computation topology of the tail domain inwhich the two newly added virtual links, the virtual node VNEj and theintra-domain topology are included, a pair of shortest disjoint pathsPin′(og, 3, j=1) and Pin′(dj, 3, j=1) from the virtual node VNEj to thetail node D is computed using the simultaneous disjoint path algorithm,a path Pin(og, 3, 1) (which is an intra-domain working path) from theBN7 to the tail node D is separated therefrom, and PKey(og, 3, 1) isgenerated as a first PathKey; and a path Pin(dj, 3, 1) (which is anintra-domain protection path) from the node BN8 to the tail node D isseparated from Pin′(dj, 3, 1), PKey(dj, 3, 1) is generated as a secondPathKey, and the first PathKey and the second PathKey are encapsulatedinto DPC_RSP(3) as a j=1^(st) pair of intra-domain paths correspondingto the j=1^(st) pair of candidate separation domain sequences in thetail domain AS(3). The DPC_RSP(3) is returned to the PCE_P.

An association request REQ_ID2-1 is included in an intra-domain pathcomputation request SUB_REQ(2) received the sub-PCE responsible forintra-domain path computation of the intermediate domain AS(ii=2), i.e.,the PCE_S(2). For the association computation request <BN3-BN5,BN4-BN6>, with reference to the description of FIG. 3(c), in theintra-domain topology of the intermediate domain AS(2), a first virtualnode VNEj is newly added as the head node of the domain AS(2), and asecond virtual node VNXj is newly added as the tail node of the domainAS(2). As a result, four newly added virtual links appear, herein thefirst newly added virtual link connects the VNEj and BN3, the secondnewly added virtual link connects the VNEj and BN4, the third newlyadded virtual link connects the BN5 and VNXj, and the fourth newly addedvirtual link connects the BN6 and VNXj. In an intra-domain pathcomputation topology of the intermediate domain in which the four newlyadded virtual links, the first virtual node VNEj, the second virtualnode VNXj, and the intra-domain topology of the intermediate domain areincluded, a pair of shortest disjoint paths Pin′(og, 2, j=1) andPin′(dj, 2, j=1) from the virtual node VNEj to VNXj is computed usingthe simultaneous disjoint path algorithm, a path Pin(og, 2, 1) (which isan intra-domain working path) from the BN3 to BN5 is separatedtherefrom, and PKey(og, 2, 1) is generated as a first PathKey. A pathPin(dj, 2, 1) (which is an intra-domain protection path) from the BN4 toBN6 is separated from Pin′(dj, 2, 1), PKey(dj, 2, 1) is generated as asecond PathKey, and the first PathKey and the second PathKey areencapsulated into DPC_RSP(2) as a j=1^(st) pair of intra-domain pathscorresponding to the j=1^(st) pair of candidate separation domainsequences in the tail domain AS(2). The DPC_RSP(2) is returned to thePCE_P.

At this point, the AS(1), the AS(2), and the AS(3) respectively acquireintra-domain paths of domains to which they belong and transmit theacquired intra-domain paths to the PCE_P.

In step 706, the PCE_P receives the SUB_RSPs(1)-(3) transmitted by thesub-PCEs(1)-(3), and configures each intra-domain path of the at leastone pair of intra-domain paths to corresponding positions in the K=2pairs of candidate separation domain sequences to form K pairs ofcandidate cross-domain separation paths; determines final cross-domainseparation paths from the K=2 pairs of candidate cross-domain separationpaths; and transmits the cross-domain separation paths to the sub-PCEwhich is used for the head node S, i.e., the PCE_S(1), as a computationresult for the cross-domain separation path computation request, and thePCE_S(1) then transmits the computation result to the head node S.

Here, the intra-domain PathKey is configured to the correspondingposition in a K^(th) pair of candidate separation domain sequences toform K=2 pairs of candidate cross-domain separation paths; herein aworking path DP(og, 1) in the first pair of candidate cross-domainseparation paths is (S, PKey(og, 1, 1), BN1, BN5, PKey(og, 2, 1), BN7,BN13, PKey(og, 4, 1), D); a protection path DP(dj, 1) in the first pairof candidate cross-domain separation paths is (S, PKey(dj, 1, 1), BN3,BN9, PKey(dj, 3, 1), BN11, BN15, PKey(dj, 4, 1), D); a working pathDP(og, 2) in the second pair of candidate cross-domain separation pathsis (S, PKey(og, 1, 2), BN2, BN6, PKey(og, 2, 2), BN8, BN14, PKey(og, 4,2), D); and a protection path DP(dj, 2) in the second pair of candidatecross-domain separation paths is (S, PKey(dj, 1, 2), BN4, BN10, PKey(dj,3, 2), BN12, BN16, PKey(dj, 4, 2), D).

The PCE_P sums path costs of the two pairs of candidate cross-domainseparation paths respectively, and takes a pair with the minimum costsum. If PM(og, j)+PM(dj, j)(j=1) is a minimum cost sum, the PCE_Pdetermines the second pair of candidate cross-domain separation pathsDP(og, 1) and DP(dj, 1) from the two pairs of candidate cross-domainseparation paths as cross-domain separation paths, encapsulates thecomputation result in DPC_RSP(S, D), and transmits the DPC_RSP(S, D) tothe PCE_S(1). The PCE_S(1) returns the DPC_RSP(S, D) in which the finalcross-domain separation path computation result is encapsulated to thehead node S which initiates the cross-domain separation path computationrequest.

It can be seen that the embodiments of the present disclosure determinea final appropriate cross-domain separation path based on thehierarchical PCE conceptual model through interaction between the parentPCE and various sub-PCEs thereof, which improves the success ratio ofthe acquisition of the cross-domain separation paths, thus ensuring theglobal optimality of path separation. Due to the use of the hierarchicalPCE conceptual model, a cross-domain end-to-end domain sequence betweena head domain and a tail domain needs not to be known in advance.

FIG. 8 is a diagram of embodiment three of a method for acquiring across-domain separation path according to the present disclosure. Theembodiment three belongs to a condition that an intra-domain pathcomputation request of a part of K pairs of candidate separation domainsequences in the intermediate domain AS(ii) is an associationcomputation request.

As shown in FIG. 8, in a current network, there are 16 boundary nodesand there are totally n=4 domains, which are AS(1), AS(2), AS(3) andAS(4) respectively. A distribution of the 16 boundary nodes in the 4domains is shown in the figure. Various domains correspond to respectivesub-PCEs, which are PCE_S(1), PCE_S(2), PCE_S(3), and PCE_S(4),respectively. In the current network, there is a parent PCE, i.e.,PCE_P, which is used to manage the four sub-PCEs. Herein, a node S is ahead node for the cross-domain path computation, and is located in thehead domain AS(1), and a node D is a destination node (tail node) forthe cross-domain path computation, and is located in the tail domainAS(4).

In step 801, the head node S sends a cross-domain separation pathcomputation request DPC_REQ(S, D) to the PCE_S(1).

In step 802, the PCE_S(1) transmits the cross-domain separation pathcomputation request to the PCE_P.

In step 803, the PCE_P receives the cross-domain separation pathcomputation request, and firstly computes K pairs of candidateseparation domain sequences using the sequential path computationaccording to an inter-domain topology consisted of ingress and egressboundary nodes and inter-domain links of various domains, herein pathsthrough which the K pairs of candidate separation domain sequences passare K pairs of candidate cross-domain separation paths.

Here, K is preset to be 2, j is initialized to be 1, and the PCE_Pcomputes a pass-through domain sequence DS(o, j=1) of a working path ina j=1^(st) pair of candidate cross-domain separation paths from a headnode S to a tail node D, herein a specific path of the domain sequenceDS(o, j=1) is a boundary node sequence (S, BN1, BN5, BN7, BN13, D)illustrated in FIG. 8; and the PCE_P computes a domain sequence DS(dj,j=1) of a protection path in the j=1^(st) pair of candidate cross-domainseparation paths from a head node S to a tail node D using the paths ofthe DS(og, 1) as a separation constraint condition using the shortestpath algorithm, herein a specific path of the domain sequence DS(dj,j=1) is a boundary node sequence (S, BN3, BN9, BN11, BN15, D)illustrated in FIG. 8.

Then, PCE_P adds 1 to j (j+1=1+1=2), and judges that j+1 is equal to 2;computes a working path DS domain sequence (og, 2) which is sub-optimalrelative to a working path domain sequence DS(og, 1) using the K-optimalpath algorithm, and uses the DS(og, 2) as a domain sequence of a workingpath in a second pair of separation paths, herein a specific path of thedomain sequence DS(og, 2) is a boundary node sequence (S, BN2, BN4, BN6,BN8, D) illustrated in FIG. 8; and the PCE_P computes a domain sequenceDS(dj, 2) of a protection path in a j=2^(nd) pair of separation pathsfrom S to D using the shortest path algorithm by taking paths of DS(og,2) as a separation constraint condition, herein a specific path of thedomain sequence DS(dj, 2) is a boundary node sequence (S, BN2, BN6, BN8,BN14, D) illustrated in FIG. 8, and the PCE_P adds 1 to j (j+1=2+1=3),and judges that j+1 is greater than K=2, and the process ends.

At this point, the PCE_P totally computes 2 pairs of candidateseparation domain sequences, each pair of candidate separation domainsequences corresponding to a candidate cross-domain separation path. Asshown in FIG. 8, the black bold solid line in the figure is the workpath in the candidate cross-domain separation paths, the black bolddotted line is the protection path in the candidate cross-domainseparation paths, and the thin dotted line represents the intra-domainpaths.

In step 804, the PCE_P traverses the 2 pairs of candidate separationdomain sequences, generates corresponding intra-domain path computationrequests for the 4 domains in the current network, and transmits theintra-domain path computation requests for the 4 domains tocorresponding sub-PCEs.

In the present embodiment, the particularity of the network topologyenables the working path domain sequence DS(og, 1) in the first pair ofcandidate separation domain sequences to coincide with the protectionpath domain sequence DS(dj, 2) in the second pair of candidateseparation domain sequences.

In the head domain AS(1), an association request REQ_ID1-1 is generated,which is <S-BN1, S-BN3> for the j=1^(st) pair of candidate separationdomain sequences, and an association request REQ_ID1-2 is generated,which is <S-BN1, S-BN2> for the j=2^(nd) pair of candidate separationdomain sequences, and two association requests REQ_ID1-1 and REQ_ID1-2are included in the intra-domain path computation request SUB_REQ(1)transmitted to the sub-PCE, i.e., PCE_S(1).

In the tail domain AS(4), an association request REQ_ID4-1 is generated,which is <BN13-D, BN15-D> for the j=1^(st) pair of candidate separationdomain sequences, and an association request REQ_ID4-2 is generated,which is <BN14-D, BN13-D> for the j=2^(nd) pair of candidate separationdomain sequences, and the above two association requests REQ_ID4-1 andREQ_ID4-2 are included in the intra-domain path computation requestSUB_REQ(4) transmitted to the sub-PCE, i.e., PCE_S(4).

In the intermediate domain AS(2), an association request REQ_ID2-1 whichis <BN6-BN8, BN5-BN7> is generated for the j=2^(nd) pair of candidateseparation domain sequences, since both DS(og, 2) and DS(dj, 2) passthrough the intermediate domain AS(2). A non-association request(independent request) REQ_ID2-2 which is <BN5-BN7> is generated for aj=1^(st) pair of candidate separation domain sequences since onlyDS(og, 1) in the DS(og, 1) and DS(dj, 1) passes through the intermediatedomain AS(2). The intra-domain path computation request SUB_REQ(2)transmitted to the sub PCE (i.e., PCE_S(2)) includes the above-mentionedassociation request REQ_ID2-1 and non-association request REQ_ID2-2.

In the intermediate domain AS(3), there is no association ornon-association request generated for the j=2^(nd) pair of candidateseparation domain sequences, since none of DS(og, 2) and DS(dj, 2)passes through the intermediate domain AS(3). A non-association requestREQ_ID3-1 which is <BN9-BN11> is generated for a j=1^(st) pair ofcandidate separation domain sequences since only DS(dj, 1) in theDS(og, 1) and DS(dj, 1) passes through the intermediate domain AS(3).The intra-domain path computation request SUB_REQ(3) transmitted to thesub-PCE (i.e., PCE_S(3)) includes the above-mentioned non-associationrequest REQ_ID3-1.

In step 805, each sub-PCE determines a type of the intra-domain pathcomputation request received by itself, acquires at least one pair ofintra-domain paths of a domain administered by itself according to thetype and domain boundary nodes carried in the intra-domain pathcomputation request, and transmits the acquired at least one pair ofintra-domain paths to the parent PCE.

Here, two association requests REQ_ID1-1 and REQ_ID1-2 are included inthe intra-domain path computation request SUB_REQ(1) received by thesub-PCE responsible for intra-domain path computation of the head domainAS(1), i.e., the PCE_S(1). Herein, for a condition that REQ_ID1-1 is<S-BN1, S-BN3>, with reference to the description of FIG. 3(a), in theintra-domain topology in the head domain AS(1), a virtual node VNXj isnewly added as a tail node in the AS(1) domain. As a result, two newlyadded virtual links appear, herein the first newly added virtual linkconnects BN1 and VNXj, and the second newly added virtual link connectsBN3 and VNXj. In the intra-domain path computation topology of the headdomain in which the two newly added virtual links, the virtual node VNXjand the intra-domain topology of the head domain are included, a pair ofshortest disjoint paths Pin′(og, 1, j=1) and Pin′(dj, 1, j=1) from thehead node S to the virtual node VNXj(j=1) is computed using thesimultaneous disjoint path algorithm, a path Pin(og, 1, 1) (which is anintra-domain working path) from the head node S to an egress boundarynode BN1 of the head domain AS(1) is separated therefrom, and PKey(og,1, 1) is generated as a first PathKey; and a path Pin(dj, 1, 1) (whichis an intra-domain protection path) from the head node S to an egressboundary node BN3 of the head domain AS(1) is separated from Pin′(dj, 1,1), PKey(dj, 1, 1) is generated as a second PathKey, and the firstPathKey and the second PathKey are encapsulated into DPC_RSP(1) as aj=1^(st) pair of intra-domain paths corresponding to the j=1^(st) pairof candidate separation domain sequences in the head domain AS(1). For acondition that REQ_ID1-2 is <S-BN1, S-BN2>, similarly, the first PathKeyand the second PathKey are separated from the pair of shortest disjointpaths using the above method of adding a virtual node, to acquirePKey(og, 1, 2) and PKey(dj, 1, 2) of a j=2^(nd) pair of intra-domainpaths corresponding to a j=2^(nd) pair of candidate separation domainsequences in the head domain AS(1), PKey(og, 1, 2) and PKey(dj, 1, 2)are encapsulated into DPC_RSP(1), and the DPC_RSP(1) is returned to thePCE_P.

Two association requests REQ_ID4-1 and REQ_ID4-2 are included in theintra-domain path computation request SUB_REQ(4) received by the sub-PCEresponsible for intra-domain path computation of the tail domain AS(4),i.e., the PCE_S(4). For a condition that REQ_ID4-1 is <BN13-D, BN15-D>,with reference to the description of FIG. 3(b), in the intra-domaintopology in the tail domain AS(4), a virtual node VNEj is newly added asa head node in the AS(4) domain. As a result, two newly added virtuallinks appear, herein the first newly added virtual link connects VNEjand BN13, and the second newly added virtual link connects VNEj andBN15. In the intra-domain path computation topology of the tail domainin which the two newly added virtual links, the virtual node VNEj andthe intra-domain topology of the tail domain are included, a pair ofshortest disjoint paths Pin′(og, 4, j=1) and Pin′(dj, 4, j=1) from thevirtual node VNEj to the tail node D is computed using the simultaneousdisjoint path algorithm, a path Pin(og, 4, 1) (which is an intra-domainworking path) from the node BN13 to the tail node D is separated fromPin′(og, 4, j=1), and (og, 4, 1) is generated as a first PathKey; and apath Pin(dj, 4, 1) (which is an intra-domain working path) from the nodeBN15 to the tail node D is separated from Pin′(dj, 4, 1), PKey(dj, 4, 1)is generated as a second PathKey, and the first PathKey and the secondPathKey are encapsulated into DPC_RSP(4) as a j=1^(st) pair ofintra-domain paths corresponding to the j=1^(st) pair of candidateseparation domain sequences in the tail domain AS(4). For a conditionthat REQ_ID4-2 is <BN14-D, BN13-D>, similarly, the intra-domain workingpath and the intra-domain protection path are separated from the pair ofshortest disjoint paths using the above method of adding a virtual node,corresponding PathKeys are generated, so as to acquire PKey(og, 4, 2)and PKey(dj, 4, 2) of a j=2^(nd) pair of intra-domain pathscorresponding to a j=2^(nd) pair of candidate separation domainsequences acquired in the tail domain AS(4), which are encapsulated intoDPC_RSP(4), and the DPC_RSP(4) is returned to the PCE_P.

An association request REQ_ID2-1 and a non-association request REQ_ID2-2are included in an intra-domain path computation request received by thesub-PCE responsible for computation of intra-domain paths of theintermediate domain AS(2), i.e., the PCE_S(2). For a condition that theassociation request REQ_ID2-1 is <BN6-BN8, BN5-BN7>, with reference tothe description of FIG. 3(c), in the intermediate domain AS(2), a firstvirtual node VNEj and a second virtual node VNXj(j=2) are added, hereinthe first virtual node VNEj is used as the head node of the domainAS(2), and the second virtual node VNXj is used as the tail node of thedomain AS(2). As a result, four newly added virtual links appear, hereinthe first newly added virtual link connects the VNEj and BN6, the secondnewly added virtual link connects the VNEj and BN5, the third newlyadded virtual link connects the BN8 and VNXj, and the fourth newly addedvirtual link connects the BN7 and VNXj. In an intra-domain pathcomputation topology of the intermediate domain in which the four newlyadded virtual links, the first virtual node VNEj, the second virtualnode VNXj, and the intra-domain topology of the intermediate domain areincluded, a pair of shortest disjoint paths Pin′(og, 2, 2) and Pin′(dj,2, 2) from the first virtual node VNEj to the second virtual node VNXjis computed using the simultaneous disjoint path algorithm, a pathPin(og, 2, 2) from the ingress boundary node BN6 to the egress boundarynode BN8 of the working path domain sequence in the j=2^(nd) pair ofcandidate separation domain sequences in the domain AS(2) is separatedfrom the pair of shortest disjoint paths, and PKey(og, 2, 2) isgenerated as a first PathKey, and a path from the ingress boundary nodeBN-en(dj, 2, 2) to the egress boundary node BN-ex(dj, 2, 2) of theprotection path domain sequence in the j=2^(nd) pair of candidateseparation domain sequences in the domain AS(2) is separated from thepair of shortest disjoint paths, and PKey(og, 2, 2) is generated as asecond PathKey, which is encapsulated into DPC_RSP(2). For a conditionthat the non-association request REQ_ID2-2 is <BN5-BN7>, intra-domainpaths from the boundary node BN5 to BN7 are computed using the shortestpath algorithm, to acquire the intra-domain paths from the boundary nodeBN5 to BN7 as Pin(og, 2, 1), and PKey(og, 2, 1) is generated as acorresponding PathKey, which is encapsulated into the SUB_RSP(2). TheDPC_RSP(2) is returned to the PCE_P.

The intra-domain path computation request received by the sub-PCEresponsible for the intra-domain path computation of the intermediatedomain AS(3), i.e., the PCE_S(3), includes a non-association request(independent request) REQ_ID3-1 which is <BN9-BN11>. For the request,the intra-domain paths of the boundary nodes BN9 to BN11 are computedusing the shortest path algorithm to acquire the intra-domain paths ofthe boundary nodes BN9 to BN11 as Pin(og, 3, 1), and PKey(og, 3, 1) isgenerated as the corresponding PathKey and is encapsulated inSUB_RSP(3). The DPC_RSP(3) is returned to the PCE_P.

In step 806, the PCE_P receives the SUB_RSPs(1)-(4) transmitted by thesub-PCEs(1)-(4), and configures each intra-domain path of the at leastone pair of intra-domain paths to corresponding positions in the K=2pairs of candidate separation domain sequences to form K pairs ofcandidate cross-domain separation paths; determines cross-domainseparation paths from the K=2 pairs of candidate cross-domain separationpaths; and transmits the cross-domain separation paths to the sub-PCEwhich is used for the head node S, i.e., the PCE_S(1), as a computationresult for the cross-domain separation path computation request, and thePCE_S(1) then transmits the computation result to the head node S.

Here, the intra-domain PathKey is configured to the correspondingposition in a K^(th) pair of candidate separation domain sequences toform K=2 pairs of candidate cross-domain separation paths; herein aworking path DP(og, 1) in the first pair of candidate cross-domainseparation paths is (S, PKey(og, 1, 1), BN1, BN5, PKey(og, 2, 1), BN7,BN13, PKey(og, 4, 1), D); a protection path DP(dj, 1) in the first pairof candidate cross-domain separation paths is (S, PKey(dj, 1, 1), BN3,BN9, PKey(dj, 3, 1), BN11, BN15, PKey(dj, 4, 1), D); a working pathDP(og, 2) in the second pair of candidate cross-domain separation pathsis (S, PKey(og, 1, 2), BN2, BN6, PKey(og, 2, 2), BN8, BN14, PKey(og, 4,2), D); and a protection path DP(dj, 2) in the second pair of candidatecross-domain separation paths is (S, PKey(og, 1, 1), BN4, BN10, PKey(dj,2, 2), BN12, BN16, PKey(og, 4, 1), D).

The PCE_P sums path costs of the two pairs of candidate cross-domainseparation paths respectively, and takes a pair with the minimum costsum. If PM(og, j)+PM(dj, j)(j=2) is a minimum cost sum, i.e., the PCE_Pdetermines that the second pair of candidate cross-domain separationpaths DPS(og, 2) and DP(dj, 2) from the two pairs of candidatecross-domain separation paths as cross-domain separation paths,encapsulates the computation result in DPC_RSP(S, D), and transmits theDPC_RSP(S, D) to the PCE_S(1). The PCE_S(1) returns the DPC_RSP(S, D) inwhich the final cross-domain separation path computation result isencapsulated to the head node S which initiates the cross-domainseparation path computation request.

It can be seen that in the embodiments of the present disclosure, when across-domain separation path computation request is received, a parentPCE in a hierarchical PCE conceptual model acquires K pairs of candidateseparation domain sequences according to a cross-domain networkabstraction topology; traverses the K pairs of candidate separationdomain sequences, generates corresponding intra-domain path computationrequests for domains through which various candidate separation domainsequences in the network pass, and transmits the intra-domain pathcomputation requests of the various domains to each sub-PCE administeredby the parent PCE; each of the at least one sub-PCE determines a type ofthe intra-domain path computation request received by itself, acquiresat least one pair of intra-domain paths administered by itself accordingto the type and domain boundary nodes carried in the intra-domain pathcomputation request, and transmits the acquired intra-domain paths tothe parent PCE; when at least one pair of intra-domain paths isreceived, the parent PCE configures each intra-domain path of the atleast one pair of intra-domain paths to a corresponding position in theK pairs of candidate separation domain sequences, to form K pairs ofcandidate cross-domain separation paths; determines one pair ofcross-domain separation paths from the K pairs of candidate cross-domainseparation paths, and transmits the cross-domain separation paths as acomputation result of the cross-domain separation path computationrequests; herein K is a positive integer. It can be seen that theembodiments of the present disclosure determine a final appropriatecross-domain separation path based on the hierarchical PCE conceptualmodel through interaction between the parent PCE and various sub-PCEsthereof, and a cross-domain end-to-end domain sequence between a headdomain and a tail domain needs not to be known in advance. Further, thesuccess ratio of the acquisition of the cross-domain separation paths(the working path and the protection path) is improved, thus ensuringthe global optimality of path separation.

Based on the above method, the embodiments of the present disclosurefurther provide a path computation element PCE, which may be used as aparent PCE in a hierarchical PCE conceptual model.

FIG. 9 is a diagram of constitution of embodiment one of a pathcomputation element according to an embodiment of the presentdisclosure. As shown in FIG. 9, the PCE includes:

a first acquisition unit 91 arranged to: when a cross-domain separationpath computation request is received, acquire K pairs of candidateseparation domain sequences according to a cross-domain networkabstraction topology;

a first generation unit 92 arranged to traverse the K pairs of candidateseparation domain sequences, generate corresponding intra-domain pathcomputation requests for domains through which various candidateseparation domain sequences in the network pass, and transmit theintra-domain path computation requests of the various domains;

a first formation unit 93 arranged to when at least one pair ofintra-domain paths for the intra-domain path computation requests arereceived, configure each intra-domain path of the at least one pair ofintra-domain paths to a corresponding position in the K pairs ofcandidate separation domain sequences, to form K pairs of candidatecross-domain separation paths;

a first determination unit 94 arranged to determine one pair ofcross-domain separation paths from the K pairs of candidate cross-domainseparation paths, and

a first transmission unit 95 arranged to transmit the cross-domainseparation paths as a computation result of the cross-domain separationpath computation request;

where K is a positive integer.

In an embodiment, the first acquisition unit 91 is arranged to:

initialize K, initialize a positive integer j to be 1, and compute aworking path domain sequence in a first pair of candidate separationdomain sequences from the K pairs of candidate separation domainsequences from a head node to a tail node of the network using a presetshortest path algorithm according to an inter-domain topology consistedof ingress and egress boundary nodes and inter-domain links of variousdomains; herein the head node and the tail node are carried in thecross-domain separation path computation request;

compute a protection path domain sequence in the first pair of candidateseparation domain sequences using the shortest path algorithm by takingpass-through paths of the working path domain sequence in the first pairof candidate separation domain sequences as a separation constraintcondition;

add 1 to j, judge whether j+1 is greater than the positive integer K,and when it is judged that j+1 is not greater than K, compute a workingpath domain sequence in a second pair of candidate separation domainsequences which is sub-optimal relative to the working path domainsequence in the first pair of candidate separation domain sequencesusing a preset K-optimal path algorithm;

compute a protection path domain sequence in the second pair ofcandidate separation domain sequences using the shortest path algorithmby taking pass-through paths of the working path domain sequence in thesecond pair of candidate separation domain sequences as a separationconstraint condition;

add 1 to j, judge whether j+1 is greater than the positive integer K,and when it is judged that j+1 is not greater than K, compute a workingpath domain sequence in a third pair of candidate separation domainsequences which is sub-optimal relative to the working path domainsequence in the second pair of candidate separation domain sequencesusing the preset K-optimal path algorithm;

compute a protection path domain sequence in the third pair of candidateseparation domain sequences using the shortest path algorithm by takingpass-through paths of the working path domain sequence in the third pairof candidate separation domain sequences as a separation constraintcondition;

and so on, until it is judged that j+1 is greater than K.

In an embodiment, the first generation unit 92 is arranged to:

for a head domain of the various domains, generate an associated pathcomputation request each time a pair of candidate separation domainsequences in the K pairs of candidate separation domain sequences istraversed; acquire an associated path computation request generated fora j1^(th) pair of candidate sequences, and determine the associated pathcomputation request as a first association request; acquire anassociated path computation request generated for a j2^(th) pair ofcandidate sequences, and determine the associated path computationrequest as a second association request; and when in the K pairs ofcandidate separation domain sequences, an egress boundary node of aworking path domain sequence in the j1^(th) pair of candidate sequencesin the head domain is the same as an egress boundary node of a workingpath domain sequence in the j2^(th) pair of candidate sequences in thehead domain, and an egress boundary node of a protection path domainsequence in the j1^(th) pair of candidate sequences in the head domainis the same as an egress boundary node of a protection path domainsequence in the j2^(th) pair of candidate sequences in the head domain,merge the first association request and the second association requestinto an associated path computation request, and use the mergedassociated path computation request as an intra-domain path computationrequest of the head domain;

for a tail domain of the various domains, generate an associated pathcomputation request each time a pair of candidate separation domainsequences in the K pairs of candidate separation domain sequences istraversed; acquire an associated path computation request generated fora j1^(th) pair of candidate sequences, and determine the associated pathcomputation request as a first association request; acquire anassociated path computation request generated for a j2^(th) pair ofcandidate sequences, and determine the associated path computationrequest as a second association request; and when in the K pairs ofcandidate separation domain sequences, an egress boundary node of aworking path domain sequence in the j1^(th) pair of candidate sequencesin the tail domain is the same as an egress boundary node of a workingpath domain sequence in the j2^(th) pair of candidate sequences in thetail domain, and an egress boundary node of a protection path domainsequence in the j1^(th) pair of candidate sequences in the tail domainis the same as an egress boundary node of a protection path domainsequence in the j2^(th) pair of candidate sequences in the tail domain,merge the first association request and the second association requestinto an associated path computation request, and use the mergedassociated path computation request as an intra-domain path computationrequest of the tail domain;

for an intermediate domain of the various domains, when a working pathdomain sequence and a protection path domain sequence in a j^(th) pairof candidate separation domain sequences in the K pairs of candidateseparation domain sequences pass through the intermediate domain,traverse the j^(th) pair of candidate separation domain sequences andgenerate an associated path computation request for the j^(th) pair ofcandidate separation domain sequences; acquire an associated pathcomputation request generated for a j1^(th) pair of candidate sequences,and determine the associated path computation request as a firstassociation request; acquire an associated path computation requestgenerated for a j2^(th) pair of candidate sequences, and determine theassociated path computation request as a second association request; andwhen in at least two pairs of candidate separation domain sequences inwhich a working path domain sequence and a protection path domainsequence pass through the intermediate domain, ingress and egressboundary nodes of a working path domain sequence in the j1^(th) pair ofcandidate sequences in the intermediate domain are correspondingly thesame as ingress and egress boundary nodes of a working path domainsequence in the j2^(th) pair of candidate sequences in the intermediatedomain, and ingress and egress boundary nodes of a protection pathdomain sequence in the j1^(th) pair of candidate sequences in theintermediate domain are correspondingly the same as ingress and egressboundary nodes of a protection path domain sequence in the j2^(th) pairof candidate sequences in the AS domain, merge the first associationrequest and the second association request into an associated pathcomputation request, and use the merged associated path computationrequest as an intra-domain path computation request of the intermediatedomain; and

for an intermediate domain of the various domains, when only one of aworking path domain sequence and a protection path domain sequence inthe j^(th) pair of candidate separation domain sequences in the K pairsof candidate separation domain sequences passes through the intermediatedomain, generate a non-associated path computation request for a domainsequence which passes through the intermediate domain; acquire anon-associated path computation request generated for a working pathdomain sequence or a protection path domain sequence of a j1^(th) pairof candidate sequences, and determine the non-associated pathcomputation request as a first non-association request; acquire anon-associated path computation request generated for a working pathdomain sequence or a protection path domain sequence of a j2^(th) pairof candidate sequences, and determine the non-associated pathcomputation request as a second non-association request; and wheningress and egress boundary nodes of a domain sequence corresponding tothe first non-associated path computation request in the intermediatedomain are the same as ingress and egress boundary nodes of a domainsequence corresponding to the second non-associated path computationrequest in the intermediate domain, merge the first non-associationrequest and the second non-association request, and use the mergednon-associated path computation request as an intra-domain pathcomputation request of the intermediate domain;

where j, j1 and j2 are positive integers, 1≤j≤K, 1≤j1≤K, 1≤j2≤K andj1≠j2.

In an embodiment, the first formation unit 93 is arranged to:

in the K pairs of candidate separation domain sequences, arrangeintra-domain paths in pass-through domains corresponding to a workingpath domain sequence in a j^(th) pair of candidate separation domainsequences to corresponding positions of a working path in the j^(th)pair of candidate separation domain sequences, and configureintra-domain paths in pass-through domains corresponding to a protectionpath domain sequence in the j^(th) pair of candidate separation domainsequences to corresponding positions of a protection path in the j^(th)pair of candidate separation domain sequences, to form the K pairs ofcandidate cross-domain separation paths;

where j is a positive integer and 1≤j≤K.

In an embodiment, the first determination unit 94 is arranged to:

compute a path cost of a working path and a path cost of a protectionpath in each of the K pairs of candidate cross-domain separation paths;

sum the path cost of the working path and the path cost of theprotection path in each pair of candidate cross-domain separation pathsto form a path cost sum; and

select candidate cross-domain separation paths with the minimum pathcost sum as the cross-domain separation paths.

In a practical application, the first acquisition unit 91, the firstgeneration unit 92, the first formation unit 93, the first determinationunit 94, and the first transmission unit 95 may each be implemented by aCentral Processing Unit (CPU), or a Digital Signal Processor (DSP), aMicro Processor Unit (MPU), or a Field Programmable Gate Array (FPGA),and the CPU, the DSP, the MPU, and the FPGA can be built into the PCE.

An embodiment of the present disclosure further provides a pathcomputation element PCE, which may be used as a sub-PCE in ahierarchical PCE conceptual model.

FIG. 10 is a diagram of constitution of embodiment two of a pathcomputation element according to an embodiment of the presentdisclosure. As shown in FIG. 10, the PCE includes:

a first transmission unit 101 arranged to, when a cross-domainseparation path computation request of a node is received, transmit thecross-domain separation path computation request;

a first determination unit 102 arranged to determine a type of anintra-domain path computation request received by itself;

a first acquisition unit 103 arranged to acquire at least one pair ofintra-domain paths in a domain administered by itself according to thetype and domain boundary nodes carried in the intra-domain pathcomputation request, and transmit the acquired intra-domain paths; and

a second transmission unit 104 arranged to receive a cross-domainseparation path computation result for the cross-domain separation pathcomputation request and transmit the received cross-domain separationpath computation result to the node.

In an embodiment, the first acquisition unit 103 is located in a headdomain, and is arranged to when determining that a type of anintra-domain path computation request received by itself is anassociated path computation request, compute intra-domain paths in thehead domain for each associated path computation request according to anegress boundary node of the head domain carried in the associated pathcomputation request using a preset simultaneous disjoint path algorithm;

the first acquisition unit 103 is located in a tail domain, and isarranged to when determining that a type of a received intra-domain pathcomputation request is an associated path computation request, computeintra-domain paths in the tail domain for each associated pathcomputation request according to an ingress boundary node of the taildomain carried in the associated path computation request using thepreset simultaneous disjoint path algorithm; and

the first acquisition unit 103 is located in an intermediate domain andis arranged to when determining that a type of a received intra-domainpath computation request includes an associated path computation requestand a non-associated path computation request, for the associated pathcomputation request, compute disjoint working path and protection pathcorresponding to the working path in the intermediate domain for eachassociation request according to ingress and egress boundary nodes ofthe intermediate domain carried in the associated path computationrequest using the preset simultaneous disjoint path algorithm, andaggregate the working path and the protection path as the intra-domainpaths; and for the non-associated path computation request, compute asingle path in the intermediate domain according to ingress and egressboundary nodes of the intermediate domain carried in the non-associationrequest using a preset shortest path algorithm and/or a K-optimal pathalgorithm, and use the single path as the intra-domain path.

Herein, the first acquisition unit 103 is located in the head domain,and is arranged to, when it is determined that the associated pathcomputation request is received, newly add a virtual node in anintra-domain topology of the head domain and newly add virtual linksthrough which the virtual node is connected to first and second egressboundary nodes; and form an intra-domain path computation topology ofthe head domain according to the virtual node and the virtual links;

in the intra-domain path computation topology of the head domain,compute a pair of shortest disjoint paths from a head node to thevirtual node in the head domain using the preset simultaneous disjointpath algorithm;

separate a path from the head node to the first egress boundary node ofthe head domain from the pair of shortest disjoint paths to form anintra-domain working path;

separate a path from the head node to the second egress boundary node ofthe head domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

use the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the head domain;

herein, the first egress boundary node is an egress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the head domain; and

the second egress boundary node is an egress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the head domain,

herein K and j are positive integers, and 1≤j≤K.

Herein, the first acquisition unit 103 is located in the tail domain andis arranged to when it is determined that the associated pathcomputation request is received, newly add a virtual node in anintra-domain topology of the tail domain and newly add virtual linksthrough which the virtual node is connected to first and second ingressboundary nodes; and form an intra-domain path computation topology ofthe tail domain according to the virtual node and the virtual links;

in the intra-domain path computation topology of the tail domain,compute a pair of shortest disjoint paths from the virtual node to atail node in the tail domain using the preset simultaneous disjoint pathalgorithm;

separate a path from the first ingress boundary node to the tail node inthe tail domain from the pair of shortest disjoint paths to form anintra-domain working path;

separate a path from the second ingress boundary node to the tail nodein the tail domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

use the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the tail domain;

herein, the first ingress boundary node is an ingress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the tail domain; and

the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the tail domain, herein Kand j are positive integers, and 1≤j≤K.

Herein, the first acquisition unit 103 is located in the intermediatedomain and is arranged to, when the associated path computation requestis received, newly add a first virtual node and a second virtual node inan intra-domain topology of the tail domain and newly add virtual linksthrough which the first virtual node is connected to first and secondingress boundary nodes and virtual links through which the secondvirtual node is connected to first and second egress boundary nodes; andform an intra-domain path computation topology of the intermediatedomain according to the first virtual node, the second virtual node andthe virtual links;

in the intra-domain path computation topology of the intermediatedomain, compute a pair of shortest disjoint paths from the first virtualnode to the second virtual node using the preset simultaneous disjointpath algorithm;

separate a path from the first ingress boundary node of the intermediatedomain to the first egress boundary node of the intermediate domain fromthe pair of shortest disjoint paths to form an intra-domain workingpath;

separate a path from the second ingress boundary node of theintermediate domain to the second egress boundary node of theintermediate domain from the pair of shortest disjoint paths to form anintra-domain protection path; and

use the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the intermediate domain;

herein, the first ingress boundary node is an ingress boundary node of aworking path domain sequence of a j^(th) pair of candidate separationdomain sequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the intermediate domain, and the first egressboundary node is an egress boundary node of the working path domainsequence in the intermediate domain; and

the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the intermediate domain, andthe second egress boundary node is an egress boundary node of theprotection path domain sequence in the intermediate domain;

herein K and j are positive integers, and 1≤j≤K.

In a practical application, each of the first transmission unit 101, thefirst determination unit 102, the first acquisition unit 103, and thesecond transmission unit 104 may be implemented by a CPU, a DSP, an MPU,or an FPGA etc.; and the DSP, the MPU, and the FPGA can be built in thePCE.

It will be understood by those skilled in the art that theimplementation functions of the various processing units in the PCEshown in FIGS. 9 and 10 can be understood with reference to theforegoing description of the method for acquiring a cross-domainseparation path. It will be understood by those skilled in the art thatthe functions of the various processing units in the PCEs shown in FIGS.9 and 10 can be implemented by a program running on a processor or by aspecific logic circuit.

Those skilled in the art should appreciate that the embodiments of thepresent disclosure can be provided as methods, systems, or computerprogram products. Therefore, forms such as hardware-only embodiments,software-only embodiments, or embodiments combining software andhardware can be used in the present disclosure. In addition, forms suchas a computer program product which is implemented on one or more ofcomputer usable storage media (including but not limited to a diskmemory and an optical memory etc.) with computer usable program codescan be used in the present disclosure.

The present disclosure is described with reference to the flowchartsand/or block diagrams of the methods, devices (systems) and computerprogram products according to the embodiments of the present disclosure.It should be understood that each flow and/or block in the flowchartsand/or block diagrams as well as a combination of the flows and/orblocks in the flowcharts and/or block diagrams can be implemented bycomputer program instructions. These computer program instructions canbe provided to a processor of a general-purpose computer, adedicated-purpose computer, an embedded processor, or other programmabledata processing devices to generate a machine. Thereby, the instructionsexecuted by the processor of the computer or other programmable dataprocessing devices generate an apparatus for implementing functionsspecified in one or more flows in the flowcharts and/or one or moreblocks in the block diagrams.

These computer program instructions can also be stored in a computerreadable memory capable of introducing a computer or other programmabledata processing devices to operate in a particular mode. Thereby, theinstructions stored in the computer readable memory generate an articleof manufacture including an instruction apparatus for implementingfunctions specified in one or more flows in the flowcharts and/or one ormore blocks in the block diagrams.

These computer program instructions can also be loaded onto a computeror other programmable data processing devices, so as to enable a seriesof operation steps to be performed on the computer or other programmabledevices to generate a computer-implemented process. Thereby, theinstructions executed on the computer or other programmable devicesprovide a step of implementing functions specified in one or more flowsin the flowcharts and/or one or more blocks in the block diagrams.

The above description is merely alternative embodiments of the presentdisclosure, and is not intended to limit the protection scope of thepresent disclosure.

INDUSTRIAL APPLICABILITY

The method for acquiring a cross-domain separation path, the relatedpath computation element, and the related computer storage medium aredisclosed according to the embodiments of the present disclosure,herein, the method includes: when a cross-domain separation pathcomputation request is received, acquiring K pairs of candidateseparation domain sequences according to a cross-domain networkabstraction topology; traversing the K pairs of candidate separationdomain sequences, generating corresponding intra-domain path computationrequests for domains through which various candidate separation domainsequences in the network pass, and transmitting the intra-domain pathcomputation requests of the various domains; when at least one pair ofintra-domain paths for the intra-domain path computation requests arereceived, configuring each intra-domain path of the at least one pair ofintra-domain paths to a corresponding position in the K pairs ofcandidate separation domain sequences, to form K pairs of candidatecross-domain separation paths; determining one pair of cross-domainseparation paths from the K pairs of candidate cross-domain separationpaths, and transmitting the cross-domain separation paths as acomputation result of the cross-domain separation path computationrequest; wherein K is a positive integer. With the embodiments of thepresent disclosure, a success ratio of acquisition of a cross-domainseparation path can be increased, and a domain sequence between a headdomain and a tail domain of an end-to-end path needs not to be known inadvance.

What is claimed is:
 1. A method for acquiring a cross-domain separationpath, comprising: when a cross-domain separation path computationrequest of a node is received, one of at least one sub-Path ComputationElement PCE which is used to administer a domain to which the nodebelongs transmitting the cross-domain separation path computationrequest; each of the at least one sub-PCE determining a type of anintra-domain path computation request received by the sub-PCE itself,acquiring at least one pair of intra-domain paths in a domainadministered by the sub-PCE itself according to the type and domainboundary nodes carried in the intra-domain path computation request, andtransmitting the acquired intra-domain paths; and receiving across-domain separation path computation result for the cross-domainseparation path computation request and transmitting the receivedcross-domain separation path computation result to the node; whereineach of the at least one sub-PCE determining a type of the intra-domainpath computation request received by the sub-PCE itself, acquiring atleast one pair of intra-domain paths in a domain to which the sub-PCEitself belongs according to the type and the domain boundary nodescarried in the intra-domain path computation request comprises: when atype of an intra-domain path computation request received by a sub-PCEwhich is used to compute intra-domain paths in a head domain is anassociated path computation request, computing intra-domain paths in thehead domain for each associated path computation request according to anegress boundary node of the head domain carried in the associated pathcomputation request using a preset simultaneous disjoint path algorithm;when a type of an intra-domain path computation request received by asub-PCE which is used to compute intra-domain paths in a tail domain isan associated path computation request, computing intra-domain paths inthe tail domain for each associated path computation request accordingto an ingress boundary node of the tail domain carried in the associatedpath computation request using the preset simultaneous disjoint pathalgorithm; and when a type of an intra-domain path computation requestreceived by a sub-PCE which is used to compute intra-domain paths in anintermediate domain comprises an associated path computation request anda non-associated path computation request, for the associated pathcomputation request, computing disjoint working path and protection pathcorresponding to the working path in the intermediate domain for eachassociation request according to ingress and egress boundary nodes ofthe intermediate domain carried in the associated path computationrequest using the preset simultaneous disjoint path algorithm, andaggregating the working path and the protection path as the intra-domainpaths; and for the non-associated path computation request, computing asingle path in the intermediate domain according to ingress and egressboundary nodes of the intermediate domain carried in the non-associationrequest using a preset shortest path algorithm and/or a K-optimal pathalgorithm, and using the single path as the intra-domain path.
 2. Themethod according to claim 1, further comprising: when the sub-PCE whichis used to compute the intra-domain paths in the head domain receivesthe associated path computation request, newly adding a virtual node inan intra-domain topology of the head domain and newly adding virtuallinks through which the virtual node is connected to first and secondegress boundary nodes; forming an intra-domain path computation topologyof the head domain according to the virtual node and the virtual links;in the intra-domain path computation topology of the head domain,computing a pair of shortest disjoint paths from a head node to thevirtual node in the head domain using the preset simultaneous disjointpath algorithm; separating a path from the head node to the first egressboundary node of the head domain from the pair of shortest disjointpaths to form an intra-domain working path; separating a path from thehead node to the second egress boundary node of the head domain from thepair of shortest disjoint paths to form an intra-domain protection path;and using the intra-domain working path and the intra-domain protectionpath as the intra-domain paths in the head domain; wherein, the firstegress boundary node is an egress boundary node of a working path domainsequence of a j^(th) pair of candidate separation domain sequences inthe K pairs of candidate separation domain sequences acquired by thesub-PCE in the head domain; and the second egress boundary node is anegress boundary node of a protection path domain sequence of the j^(th)pair of candidate separation domain sequences in the K pairs ofcandidate separation domain sequences acquired by the sub-PCE in thehead domain, wherein K and j are positive integers, and 1≤j≤K.
 3. Themethod according to claim 1, further comprising: when the sub-PCE whichis used to compute the intra-domain paths in the tail domain receivesthe associated path computation request, newly adding a virtual node inan intra-domain topology of the tail domain and newly adding virtuallinks through which the virtual node is connected to first and secondingress boundary nodes; forming an intra-domain path computationtopology of the tail domain according to the virtual node and thevirtual links; in the intra-domain path computation topology of the taildomain, computing a pair of shortest disjoint paths from the virtualnode to a tail node in the tail domain using the preset simultaneousdisjoint path algorithm; separating a path from the first ingressboundary node to the tail node in the tail domain from the pair ofshortest disjoint paths to form an intra-domain working path; separatinga path from the second ingress boundary node to the tail node in thetail domain from the pair of shortest disjoint paths to form anintra-domain protection path; and using the intra-domain working pathand the intra-domain protection path as the intra-domain paths in thetail domain; wherein, the first ingress boundary node is an ingressboundary node of a working path domain sequence of a j^(th) pair ofcandidate separation domain sequences in the K pairs of candidateseparation domain sequences acquired by the sub-PCE in the tail domain;and the second ingress boundary node is an ingress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the tail domain, wherein Kand j are positive integers, and 1≤j≤K.
 4. The method according to claim1, further comprising: when the sub-PCE which is used to compute theintra-domain paths in the intermediate domain receives the associatedpath computation request, newly adding a first virtual node and a secondvirtual node in an intra-domain topology of the tail domain and newlyadding virtual links through which the first virtual node is connectedto first and second ingress boundary nodes and virtual links throughwhich the second virtual node is connected to first and second egressboundary nodes; forming an intra-domain path computation topology of theintermediate domain according to the first virtual node, the secondvirtual node and the virtual links; in the intra-domain path computationtopology of the intermediate domain, computing a pair of shortestdisjoint paths from the first virtual node to the second virtual nodeusing the preset simultaneous disjoint path algorithm; separating a pathfrom the first ingress boundary node of the intermediate domain to thefirst egress boundary node of the intermediate domain from the pair ofshortest disjoint paths to form an intra-domain working path; separatinga path from the second ingress boundary node of the intermediate domainto the second egress boundary node of the intermediate domain from thepair of shortest disjoint paths to form an intra-domain protection path;and using the intra-domain working path and the intra-domain protectionpath as the intra-domain paths in the intermediate domain; wherein, thefirst ingress boundary node is an ingress boundary node of a workingpath domain sequence of a j^(th) pair of candidate separation domainsequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the intermediate domain, and the first egressboundary node is an egress boundary node of the working path domainsequence in the intermediate domain; and the second ingress boundarynode is an ingress boundary node of a protection path domain sequence ofthe j^(th) pair of candidate separation domain sequences in the K pairsof candidate separation domain sequences acquired by the sub-PCE in theintermediate domain, and the second egress boundary node is an egressboundary node of the protection path domain sequence in the intermediatedomain; wherein K and j are positive integers, and 1≤j≤K.
 5. A computerstorage medium, in which a second set of computer-executableinstructions are stored, wherein the second set of computer-executableinstructions are used to perform the method for acquiring a cross-domainseparation path according to claim
 1. 6. A path computation element,comprising a memory storing instructions and a processor which isarranged to execute the instructions in the memory to: when across-domain separation path computation request of a node is received,transmit the cross-domain separation path computation request; determinea type of an intra-domain path computation request received by itself;acquire at least one pair of intra-domain paths in a domain administeredby itself according to the type and domain boundary nodes carried in theintra-domain path computation request, and transmit the acquiredintra-domain paths; and receive a cross-domain separation pathcomputation result for the cross-domain separation path computationrequest and transmit the received cross-domain separation pathcomputation result to the node; wherein, the processor is arranged to:when the path computation element is located in a head domain, and whendetermining that a type of an intra-domain path computation requestreceived by itself is an associated path computation request, computeintra-domain paths in the head domain for each associated pathcomputation request according to an egress boundary node of the headdomain carried in the associated path computation request using a presetsimultaneous disjoint path algorithm; when the path computation elementis located in a tail domain, and when determining that a type of areceived intra-domain path computation request is an associated pathcomputation request, compute intra-domain paths in the tail domain foreach associated path computation request according to an ingressboundary node of the tail domain carried in the associated pathcomputation request using the preset simultaneous disjoint pathalgorithm; and when the path computation element is located in anintermediate domain and when determining that a type of a receivedintra-domain path computation request comprises an associated pathcomputation request and a non-associated path computation request, forthe associated path computation request, compute disjoint working pathand protection path corresponding to the working path in theintermediate domain for each association request according to ingressand egress boundary nodes of the intermediate domain carried in theassociated path computation request using the preset simultaneousdisjoint path algorithm, and aggregate the working path and theprotection path as the intra-domain paths and for the non-associatedpath computation request, compute a single path in the intermediatedomain according to ingress and egress boundary nodes of theintermediate domain carried in the non-association request using apreset shortest path algorithm and/or a K-optimal path algorithm, anduse the single path as the intra-domain path.
 7. The path computationelement according to claim 6, wherein, the processor is arranged to:when the path computation element is located in the head domain, andwhen it is determined that the associated path computation request isreceived, newly add a virtual node in an intra-domain topology of thehead domain and newly add virtual links through which the virtual nodeis connected to first and second egress boundary nodes; form anintra-domain path computation topology of the head domain according tothe virtual node and the virtual links; in the intra-domain pathcomputation topology of the head domain, compute a pair of shortestdisjoint paths from a head node to the virtual node in the head domainusing the preset simultaneous disjoint path algorithm; separate a pathfrom the head node to the first egress boundary node of the head domainfrom the pair of shortest disjoint paths to form an intra-domain workingpath; separate a path from the head node to the second egress boundarynode of the head domain from the pair of shortest disjoint paths to forman intra-domain protection path; and use the intra-domain working pathand the intra-domain protection path as the intra-domain paths in thehead domain; wherein, the first egress boundary node is an egressboundary node of a working path domain sequence of a j^(th) pair ofcandidate separation domain sequences in the K pairs of candidateseparation domain sequences acquired by the sub-PCE in the head domain;and the second egress boundary node is an egress boundary node of aprotection path domain sequence of the j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the head domain, wherein Kand j are positive integers, and 1≤j≤K.
 8. The path computation elementaccording to claim 6, wherein, the processor is arranged to: when thepath computation element is located in the tail domain and when it isdetermined that the associated path computation request is received,newly add a virtual node in an intra-domain topology of the tail domainand newly add virtual links through which the virtual node is connectedto first and second ingress boundary nodes; form an intra-domain pathcomputation topology of the tail domain according to the virtual nodeand the virtual links; in the intra-domain path computation topology ofthe tail domain, compute a pair of shortest disjoint paths from thevirtual node to a tail node in the tail domain using the presetsimultaneous disjoint path algorithm; separate a path from the firstingress boundary node to the tail node in the tail domain from the pairof shortest disjoint paths to form an intra-domain working path;separate a path from the second ingress boundary node to the tail nodein the tail domain from the pair of shortest disjoint paths to form anintra-domain protection path; and use the intra-domain working path andthe intra-domain protection path as the intra-domain paths in the taildomain; wherein, the first ingress boundary node is an ingress boundarynode of a working path domain sequence of a j^(th) pair of candidateseparation domain sequences in the K pairs of candidate separationdomain sequences acquired by the sub-PCE in the tail domain; and thesecond ingress boundary node is an ingress boundary node of a protectionpath domain sequence of the j^(th) pair of candidate separation domainsequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the tail domain, wherein K and j are positiveintegers, and 1≤j≤K.
 9. The path computation element according to claim6, wherein, the processor is arranged to: when the path computationelement is located in the intermediate domain and when the associatedpath computation request is received, newly add a first virtual node anda second virtual node in an intra-domain topology of the tail domain andnewly add virtual links through which the first virtual node isconnected to first and second ingress boundary nodes and virtual linksthrough which the second virtual node is connected to first and secondegress boundary nodes; form an intra-domain path computation topology ofthe intermediate domain according to the first virtual node, the secondvirtual node and the virtual links; in the intra-domain path computationtopology of the intermediate domain, compute a pair of shortest disjointpaths from the first virtual node to the second virtual node using thepreset simultaneous disjoint path algorithm; separate a path from thefirst ingress boundary node of the intermediate domain to the firstegress boundary node of the intermediate domain from the pair ofshortest disjoint paths to form an intra-domain working path; separate apath from the second ingress boundary node of the intermediate domain tothe second egress boundary node of the intermediate domain from the pairof shortest disjoint paths to form an intra-domain protection path; anduse the intra-domain working path and the intra-domain protection pathas the intra-domain paths in the intermediate domain; wherein, the firstingress boundary node is an ingress boundary node of a working pathdomain sequence of a j^(th) pair of candidate separation domainsequences in the K pairs of candidate separation domain sequencesacquired by the sub-PCE in the intermediate domain, and the first egressboundary node is an egress boundary node of the working path domainsequence in the intermediate domain; and the second ingress boundarynode is an ingress boundary node of a protection path domain sequence ofthe j^(th) pair of candidate separation domain sequences in the K pairsof candidate separation domain sequences acquired by the sub-PCE in theintermediate domain, and the second egress boundary node is an egressboundary node of the protection path domain sequence in the intermediatedomain; wherein K and j are positive integers, and 1≤j≤K.